product and sales fixers

Backend/ERPCore/Controllers/ItemImagesController.cs

@@ -0,0 +1,64 @@
+using ERPCore.Dtos.Items;
+using ERPCore.Infra.Auth;
+using ERPCore.Services;
+using ERPCore.Services.Interfaces;
+using Microsoft.AspNetCore.Authorization;
+using Microsoft.AspNetCore.Mvc;
+
+namespace ERPCore.Controllers;
+
+/// <summary>Item photos. Same access as the item master itself.</summary>
+[Route("api/v1/items/{itemId:int}/images")]
+[Authorize(Policy = NavPolicies.Prefix + "products")]
+public sealed class ItemImagesController : ApiControllerBase
+{
+    private readonly IItemImageService _images;
+    private readonly ICurrentUser _currentUser;
+
+    public ItemImagesController(IItemImageService images, ICurrentUser currentUser)
+    {
+        _images = images;
+        _currentUser = currentUser;
+    }
+
+    [HttpGet]
+    [ProducesResponseType(typeof(List<ItemImageDto>), StatusCodes.Status200OK)]
+    [ProducesResponseType(StatusCodes.Status404NotFound)]
+    public async Task<ActionResult<List<ItemImageDto>>> List(int itemId, CancellationToken ct)
+        => Ok(await _images.ListAsync(itemId, ct));
+
+    /// <summary>Upload one image (multipart <c>file</c>). 422 CONFIG_DISABLED while item images are off.</summary>
+    [HttpPost]
+    [RequestSizeLimit(ItemImageService.MaxSizeBytes + 64 * 1024)]
+    [ProducesResponseType(typeof(ItemImageDto), StatusCodes.Status201Created)]
+    [ProducesResponseType(StatusCodes.Status404NotFound)]
+    [ProducesResponseType(StatusCodes.Status413PayloadTooLarge)]
+    [ProducesResponseType(StatusCodes.Status422UnprocessableEntity)]
+    public async Task<ActionResult<ItemImageDto>> Upload(int itemId, IFormFile file, CancellationToken ct)
+    {
+        await using var stream = file.OpenReadStream();
+        var result = await _images.UploadAsync(itemId, stream, file.FileName, file.ContentType, _currentUser.AuditUserId, ct);
+        return Created($"/api/v1/items/{itemId}/images/{result.ItemImageId}", result);
+    }
+
+    /// <summary>The image bytes, served inline so an &lt;img&gt; can point straight at it.</summary>
+    [HttpGet("{itemImageId:int}/content")]
+    [ProducesResponseType(StatusCodes.Status200OK)]
+    [ProducesResponseType(StatusCodes.Status404NotFound)]
+    public async Task<IActionResult> Content(int itemId, int itemImageId, CancellationToken ct)
+    {
+        var (content, contentType) = await _images.OpenAsync(itemId, itemImageId, ct);
+        // Stored files are immutable (new upload ⇒ new id), so the browser may cache them.
+        Response.Headers.CacheControl = "private, max-age=86400";
+        return File(content, contentType);
+    }
+
+    [HttpDelete("{itemImageId:int}")]
+    [ProducesResponseType(StatusCodes.Status204NoContent)]
+    [ProducesResponseType(StatusCodes.Status404NotFound)]
+    public async Task<IActionResult> Delete(int itemId, int itemImageId, CancellationToken ct)
+    {
+        await _images.DeleteAsync(itemId, itemImageId, ct);
+        return NoContent();
+    }
+}

Backend/ERPCore/Controllers/ItemsController.cs

@@ -40,8 +40,11 @@ public sealed class ItemsController : ApiControllerBase
         [FromQuery] int? categoryId,
         [FromQuery] int? subCategoryId,
         [FromQuery] int? brandId,
+        [FromQuery] TrackingMode? trackingMode,
+        [FromQuery] StockNature? stockNature,
+        [FromQuery] ItemStockFilter? stock,
         CancellationToken ct)
-        => Ok(await _items.GetOverviewAsync(query, status, categoryId, subCategoryId, brandId, ct));
+        => Ok(await _items.GetOverviewAsync(query, status, categoryId, subCategoryId, brandId, trackingMode, stockNature, stock, ct));
 
     /// <summary>Barcode/RFID lookup — matches an item's barcode/SKU, or a batch/serial
     /// barcode/no (optionally scoped to <paramref name="itemId"/> first).</summary>

Backend/ERPCore/Controllers/ProductConfigController.cs

@@ -45,5 +45,4 @@ public sealed class ProductConfigController : ApiControllerBase
         var result = await _config.UpdateAsync(request, expected, ct);
         SetETag(result.RowVersion);
         return Ok(result.Value);
-    }
-}
+    }}

Backend/ERPCore/Controllers/SalesConfigController.cs

@@ -0,0 +1,46 @@
+using Microsoft.AspNetCore.Authorization;
+using ERPCore.Infra.Auth;
+using ERPCore.Dtos.Config;
+using ERPCore.Services.Interfaces;
+using Microsoft.AspNetCore.Mvc;
+
+namespace ERPCore.Controllers;
+
+/// <summary>
+/// Sales configuration endpoints — the singleton "allow cash customer" toggle.
+/// <para>
+/// <b>Authorization:</b> gated on the Sales nav policy (the New Sale form has to read it), same
+/// Phase-1 posture as <see cref="BranchConfigController"/> — any Sales user can flip the flag
+/// until per-endpoint RBAC lands.
+/// </para>
+/// </summary>
+[Route("api/v1/sales-config")]
+[Authorize(Policy = NavPolicies.Prefix + "sales")]
+public sealed class SalesConfigController : ApiControllerBase
+{
+    private readonly ISalesConfigService _config;
+
+    public SalesConfigController(ISalesConfigService config) => _config = config;
+
+    [HttpGet]
+    [ProducesResponseType(typeof(SalesConfigDto), StatusCodes.Status200OK)]
+    public async Task<ActionResult<SalesConfigDto>> Get(CancellationToken ct)
+    {
+        var result = await _config.GetAsync(ct);
+        SetETag(result.RowVersion);
+        return Ok(result.Value);
+    }
+
+    [HttpPut]
+    [ProducesResponseType(typeof(SalesConfigDto), StatusCodes.Status200OK)]
+    [ProducesResponseType(StatusCodes.Status400BadRequest)]
+    [ProducesResponseType(StatusCodes.Status412PreconditionFailed)]
+    public async Task<ActionResult<SalesConfigDto>> Update(
+        [FromBody] UpdateSalesConfigRequest request, CancellationToken ct)
+    {
+        var expected = RequireIfMatch();
+        var result = await _config.UpdateAsync(request, expected, ct);
+        SetETag(result.RowVersion);
+        return Ok(result.Value);
+    }
+}

Backend/ERPCore/Controllers/SalesInvoicesController.cs

@@ -14,11 +14,60 @@ public sealed class SalesInvoicesController : ApiControllerBase
 {
     private readonly ISalesInvoiceService _invoices;
     private readonly ISalesInvoicePaymentService _payments;
+    private readonly ISalesPricingService _pricing;
+    private readonly ISalesDomainService _sales;
+    private readonly IStockService _stock;
 
-    public SalesInvoicesController(ISalesInvoiceService invoices, ISalesInvoicePaymentService payments)
+    public SalesInvoicesController(
+        ISalesInvoiceService invoices, ISalesInvoicePaymentService payments, ISalesPricingService pricing,
+        ISalesDomainService sales, IStockService stock)
     {
         _invoices = invoices;
         _payments = payments;
+        _pricing = pricing;
+        _sales = sales;
+        _stock = stock;
+    }
+
+    // Lets the New Sale form warn, per line, when qty exceeds the stock a sale can issue — under
+    // the "sales" policy, since sales users may not hold the "stock" nav permission. Non-stocked
+    // items (services) are never short, so they report IsStocked = false and no limit.
+    [HttpGet("stock-availability")]
+    [ProducesResponseType(typeof(SalesStockAvailabilityDto), StatusCodes.Status200OK)]
+    [ProducesResponseType(StatusCodes.Status404NotFound)]
+    public async Task<ActionResult<SalesStockAvailabilityDto>> StockAvailability(
+        [FromQuery] int itemId, [FromQuery] int warehouseId, CancellationToken ct)
+    {
+        bool isStocked;
+        try
+        {
+            isStocked = await _sales.IsStockedItemAsync(itemId, ct);
+        }
+        catch (InvalidOperationException)
+        {
+            return NotFound();
+        }
+        var available = isStocked ? (await _stock.GetOnHandAsync(itemId, warehouseId, ct)).Available : 0m;
+        return Ok(new SalesStockAvailabilityDto(itemId, warehouseId, isStocked, available));
+    }
+
+    // Lets the New Sale form pre-fill Unit price for items with no flat selling price, using the
+    // same resolution the server applies on save.
+    [HttpGet("suggested-price")]
+    [ProducesResponseType(typeof(SalesSuggestedPriceDto), StatusCodes.Status200OK)]
+    [ProducesResponseType(StatusCodes.Status404NotFound)]
+    public async Task<ActionResult<SalesSuggestedPriceDto>> SuggestedPrice(
+        [FromQuery] int itemId, [FromQuery] int warehouseId, CancellationToken ct)
+    {
+        try
+        {
+            var price = await _pricing.ResolveAsync(itemId, warehouseId, null, false, ct);
+            return Ok(new SalesSuggestedPriceDto(itemId, warehouseId, price.UnitPrice, price.PriceSource));
+        }
+        catch (InvalidOperationException)
+        {
+            return NotFound();
+        }
     }
 
     [HttpGet]

Backend/ERPCore/Controllers/WarrantyPeriodsController.cs

@@ -0,0 +1,44 @@
+using ERPCore.Domain.Enums;
+using ERPCore.Dtos.Items;
+using ERPCore.Infra.Auth;
+using ERPCore.Services.Interfaces;
+using Microsoft.AspNetCore.Authorization;
+using Microsoft.AspNetCore.Mvc;
+
+namespace ERPCore.Controllers;
+
+/// <summary>Custom warranty period master — managed under Products like Item Variants.</summary>
+[Route("api/v1/warranty-periods")]
+[Authorize(Policy = NavPolicies.Prefix + "products")]
+public sealed class WarrantyPeriodsController : ApiControllerBase
+{
+    private readonly IWarrantyPeriodService _periods;
+
+    public WarrantyPeriodsController(IWarrantyPeriodService periods) => _periods = periods;
+
+    /// <summary>Custom periods only (defaults are fixed); filter <c>status=Active</c> for selectable rows.</summary>
+    [HttpGet]
+    [ProducesResponseType(typeof(List<WarrantyPeriodDto>), StatusCodes.Status200OK)]
+    public async Task<ActionResult<List<WarrantyPeriodDto>>> List([FromQuery] EntityStatus? status, CancellationToken ct)
+        => Ok(await _periods.ListAsync(status, ct));
+
+    [HttpPost]
+    [ProducesResponseType(typeof(WarrantyPeriodDto), StatusCodes.Status201Created)]
+    [ProducesResponseType(StatusCodes.Status409Conflict)]
+    [ProducesResponseType(StatusCodes.Status422UnprocessableEntity)]
+    public async Task<ActionResult<WarrantyPeriodDto>> Create([FromBody] CreateWarrantyPeriodRequest request, CancellationToken ct)
+    {
+        var result = await _periods.CreateAsync(request.Months!.Value, ct);
+        return Created($"/api/v1/warranty-periods/{result.WarrantyPeriodId}", result);
+    }
+
+    /// <summary>Deactivate/reactivate. Never hard-deleted (FR-MD-08).</summary>
+    [HttpPatch("{warrantyPeriodId:int}/status")]
+    [ProducesResponseType(StatusCodes.Status204NoContent)]
+    [ProducesResponseType(StatusCodes.Status404NotFound)]
+    public async Task<IActionResult> SetStatus(int warrantyPeriodId, [FromBody] UpdateWarrantyPeriodStatusRequest request, CancellationToken ct)
+    {
+        await _periods.SetStatusAsync(warrantyPeriodId, request.Status, ct);
+        return NoContent();
+    }
+}

Backend/ERPCore/Domain/Entities/ItemImage.cs

@@ -0,0 +1,27 @@
+namespace ERPCore.Domain.Entities;
+
+/// <summary>
+/// A product photo attached to an item. Like <see cref="EmployeeDocument"/>, the file lives
+/// behind <see cref="Infra.Storage.IFileStorageService"/> under a server-generated name and is
+/// only reachable through the authenticated items API — never a static path. Only uploadable
+/// while <see cref="ProductConfig.ItemImagesEnabled"/> is on; existing images stay readable
+/// after the flag is switched off (reads are never gated).
+/// </summary>
+public class ItemImage
+{
+    public int ItemImageId { get; set; }
+    public int ItemId { get; set; }
+    public Item? Item { get; set; }
+
+    public string OriginalFileName { get; set; } = string.Empty;
+    public string StoredFileName { get; set; } = string.Empty;
+    public string RelativePath { get; set; } = string.Empty;
+    public string ContentType { get; set; } = string.Empty;
+    public long SizeBytes { get; set; }
+
+    /// <summary>Display order; the lowest is the item's main image.</summary>
+    public int SortOrder { get; set; }
+
+    public int UploadedBy { get; set; }
+    public DateTime UploadedAt { get; set; }
+}

Backend/ERPCore/Domain/Entities/ProductConfig.cs

@@ -31,6 +31,26 @@ public class ProductConfig
     public bool BatchListsEnabled { get; set; } = true;
     public bool WarrantyPeriodsEnabled { get; set; } = true;
 
+    /// <summary>
+    /// Lets the item create screen add a new item variant (item type) on the spot, instead
+    /// of only picking from the Item Variants master. Advisory like <see cref="ItemTypesEnabled"/>
+    /// - it gates a UI shortcut; the Item Variants master itself stays available either way.
+    /// </summary>
+    public bool CustomVariantsEnabled { get; set; }
+
+    /// <summary>
+    /// Allows photos to be uploaded to items (<see cref="ItemImage"/>). Enforced on upload
+    /// (<c>CONFIG_DISABLED</c>); images added earlier stay viewable when switched off.
+    /// </summary>
+    public bool ItemImagesEnabled { get; set; }
+
+    /// <summary>
+    /// Lets items use the active <see cref="WarrantyPeriod"/> master rows alongside the default
+    /// <see cref="Enums.WarrantyPeriods.AllowedMonths"/>. Enforced on item writes. The periods
+    /// themselves are managed under Products, not here.
+    /// </summary>
+    public bool CustomWarrantyPeriodsEnabled { get; set; }
+
     public DateTime? UpdatedAt { get; set; }
 
     public int? UpdatedBy { get; set; }

Backend/ERPCore/Domain/Entities/SalesConfig.cs

@@ -0,0 +1,61 @@
+namespace ERPCore.Domain.Entities;
+
+/// <summary>
+/// Sales configuration — a singleton row (single-tenant, docs/00-CORE §1), same shape as
+/// <see cref="BranchConfig"/>. When <see cref="AllowCashCustomer"/> is on, sales documents may
+/// be raised against the generic "Cash Customer" (<see cref="CashCustomerId"/>) and the New Sale
+/// form defaults to it; when off, a real customer must be picked and the cash customer is
+/// rejected server-side (see SalesDomainService.ValidateSalesHeaderAsync).
+/// </summary>
+public class SalesConfig
+{
+    /// <summary>Always 1 - the singleton row's id.</summary>
+    public const int SingletonId = 1;
+
+    public int ConfigId { get; set; }
+
+    public bool AllowCashCustomer { get; set; }
+
+    /// <summary>The Customer row used for cash (walk-in, unnamed) sales. Created on first
+    /// enabling <see cref="AllowCashCustomer"/> and kept afterwards, so switching the option
+    /// off and on again reuses the same customer (and its sales history).</summary>
+    public int? CashCustomerId { get; set; }
+    public Customer? CashCustomer { get; set; }
+
+    /// <summary>When on, sales invoice lines may carry a free quantity (the New Sale "Free"
+    /// column); when off, the column is hidden and a free qty above zero is rejected server-side
+    /// (see SalesInvoiceService.BuildLinesAsync). Defaults on, matching the behaviour before
+    /// this option existed.</summary>
+    public bool AllowFreeItems { get; set; } = true;
+
+    /// <summary>When on, sales invoice lines may carry a line discount (the New Sale "Disc %"
+    /// column); when off, the column is hidden and a discount above zero is rejected server-side
+    /// (see SalesInvoiceService.BuildLinesAsync). Defaults on, matching the behaviour before
+    /// this option existed.</summary>
+    public bool AllowDiscounts { get; set; } = true;
+
+    /// <summary>When on, posting a sale (invoice, slip, bundle) may issue more than the stock on
+    /// hand — the shortfall drives on-hand negative (see FifoCostingService.ConsumeAsync) and the
+    /// pre-post check reports it as a warning only. When off (default), posting is blocked with
+    /// STOCK_NEGATIVE_BLOCKED until stock covers every line.</summary>
+    public bool AllowOverStockSale { get; set; }
+
+    /// <summary>When on (default) and no <see cref="DefaultWarehouseId"/> is saved, New Sale shows
+    /// a Warehouse picker. When off, a default must be saved.</summary>
+    public bool AllowWarehouseSelection { get; set; } = true;
+
+    /// <summary>Default sales warehouse. Whenever set, New Sale shows only this warehouse (locked)
+    /// and every sales invoice (header and lines) is forced onto it server-side (see
+    /// SalesDomainService.GetForcedSalesWarehouseIdAsync). Required while
+    /// <see cref="AllowWarehouseSelection"/> is off; clearing it brings the picker back.</summary>
+    public int? DefaultWarehouseId { get; set; }
+    public Warehouse? DefaultWarehouse { get; set; }
+
+    public DateTime? UpdatedAt { get; set; }
+
+    public int? UpdatedBy { get; set; }
+    public User? UpdatedByUser { get; set; }
+
+    /// <summary>PostgreSQL xmin-backed optimistic concurrency token (ETag source).</summary>
+    public uint RowVersion { get; set; }
+}

Backend/ERPCore/Domain/Entities/User.cs

@@ -15,6 +15,12 @@ public class User
     /// <summary>Seeded fallback actor for unauthenticated/system operations.</summary>
     public const int SystemUserId = 1;
 
+    /// <summary>
+    /// Username prefix of a permanently deleted login whose row is kept only because history
+    /// (audit log, documents) still references it. Such rows are hidden from user management.
+    /// </summary>
+    public const string DeletedUsernamePrefix = "deleted-user-";
+
     public int UserId { get; set; }
     public string Username { get; set; } = string.Empty;
     public string DisplayName { get; set; } = string.Empty;

Backend/ERPCore/Domain/Entities/WarrantyPeriod.cs

@@ -0,0 +1,23 @@
+using ERPCore.Domain.Enums;
+
+namespace ERPCore.Domain.Entities;
+
+/// <summary>
+/// Custom warranty period master — a coverage length offered to items alongside the fixed
+/// defaults in <see cref="WarrantyPeriods.AllowedMonths"/>, while
+/// <see cref="ProductConfig.CustomWarrantyPeriodsEnabled"/> is on.
+/// <para>
+/// Always in months (a "2 year" entry is stored as 24). Like <see cref="ItemType"/> it is
+/// deliberately unlinked: an item stores the number of months itself, not a reference, so
+/// deactivating a period only stops it being offered — items already using it keep it.
+/// The length is immutable (no PUT); a different length is a different row.
+/// </para>
+/// </summary>
+public class WarrantyPeriod
+{
+    public int WarrantyPeriodId { get; set; }
+    public int Months { get; set; }
+    public EntityStatus Status { get; set; } = EntityStatus.Active;
+    public DateTime CreatedAt { get; set; }
+    public DateTime? UpdatedAt { get; set; }
+}

Backend/ERPCore/Dtos/Config/ProductConfigDtos.cs

@@ -12,6 +12,8 @@ namespace ERPCore.Dtos.Config;
 public sealed record ProductConfigDto(
     bool SubcategoriesEnabled, bool BrandsEnabled, bool ItemTypesEnabled,
     bool SellingPricesEnabled, bool SerialNumbersEnabled, bool BatchListsEnabled, bool WarrantyPeriodsEnabled,
+    bool CustomVariantsEnabled, bool ItemImagesEnabled,
+    bool CustomWarrantyPeriodsEnabled,
     DateTime? UpdatedAt, int? UpdatedBy);
 
 /// <summary>
@@ -32,4 +34,7 @@ public sealed class UpdateProductConfigRequest
     [Required] public bool? SerialNumbersEnabled { get; set; }
     [Required] public bool? BatchListsEnabled { get; set; }
     [Required] public bool? WarrantyPeriodsEnabled { get; set; }
+    [Required] public bool? CustomVariantsEnabled { get; set; }
+    [Required] public bool? ItemImagesEnabled { get; set; }
+    [Required] public bool? CustomWarrantyPeriodsEnabled { get; set; }
 }

Backend/ERPCore/Dtos/Config/SalesConfigDtos.cs

@@ -0,0 +1,25 @@
+using System.ComponentModel.DataAnnotations;
+
+namespace ERPCore.Dtos.Config;
+
+/// <summary>Sales configuration resource. <c>CashCustomerId</c>/<c>CashCustomerName</c> identify
+/// the generic cash customer (null until the option has been switched on at least once).</summary>
+public sealed record SalesConfigDto(
+    bool AllowCashCustomer, int? CashCustomerId, string? CashCustomerName, bool AllowFreeItems, bool AllowDiscounts, bool AllowOverStockSale,
+    bool AllowWarehouseSelection, int? DefaultWarehouseId, string? DefaultWarehouseName, DateTime? UpdatedAt, int? UpdatedBy);
+
+/// <summary>
+/// Full replacement of the flags. <c>UpdatedBy</c> is derived from the token, never posted.
+/// Nullable bool so an omitted flag is a 400 rather than silently binding to <c>false</c>
+/// (same reasoning as <see cref="UpdateBranchConfigRequest"/>).
+/// </summary>
+public sealed class UpdateSalesConfigRequest
+{
+    [Required] public bool? AllowCashCustomer { get; set; }
+    [Required] public bool? AllowFreeItems { get; set; }
+    [Required] public bool? AllowDiscounts { get; set; }
+    [Required] public bool? AllowOverStockSale { get; set; }
+    [Required] public bool? AllowWarehouseSelection { get; set; }
+    /// <summary>Required when <see cref="AllowWarehouseSelection"/> is false.</summary>
+    public int? DefaultWarehouseId { get; set; }
+}

Backend/ERPCore/Dtos/Items/ItemImageDtos.cs

@@ -0,0 +1,7 @@
+namespace ERPCore.Dtos.Items;
+
+/// <summary>An item photo's metadata. The bytes are served by
+/// <c>GET /items/{itemId}/images/{itemImageId}/content</c>.</summary>
+public sealed record ItemImageDto(
+    int ItemImageId, int ItemId, string FileName, string ContentType, long SizeBytes,
+    int SortOrder, DateTime UploadedAt);

Backend/ERPCore/Dtos/Items/ItemOverviewDtos.cs

@@ -16,3 +16,12 @@ public sealed record ItemOverviewDto(
     decimal StockQty, decimal StockValue, bool IsLowStock,
     DateTime? LastPurchaseDate, int? LastSupplierId, string? LastSupplierName,
     decimal SalesQtyLast30Days);
+
+/// <summary>Stock-state filter for the Items overview. <c>LowStock</c> uses the same rule
+/// as <see cref="ItemOverviewDto.IsLowStock"/>: on-hand at or below any warehouse's reorder point.</summary>
+public enum ItemStockFilter
+{
+    InStock,
+    OutOfStock,
+    LowStock
+}

Backend/ERPCore/Dtos/Items/WarrantyPeriodDtos.cs

@@ -0,0 +1,17 @@
+using System.ComponentModel.DataAnnotations;
+using ERPCore.Domain.Enums;
+
+namespace ERPCore.Dtos.Items;
+
+public sealed record WarrantyPeriodDto(int WarrantyPeriodId, int Months, EntityStatus Status, DateTime CreatedAt, DateTime? UpdatedAt);
+
+/// <summary>A new custom length, always in months (the client converts years).</summary>
+public sealed class CreateWarrantyPeriodRequest
+{
+    [Required] public int? Months { get; set; }
+}
+
+public sealed class UpdateWarrantyPeriodStatusRequest
+{
+    [Required] public EntityStatus Status { get; set; }
+}

Backend/ERPCore/Dtos/Sales/SalesInvoiceDtos.cs

@@ -44,6 +44,14 @@ public sealed record SalesInvoicePostingCheckDto(
     int SalesInvoiceId, string InvoiceNo, SalesInvoiceStatus Status, bool CanPost,
     IReadOnlyList<SalesInvoicePostingIssueDto> Issues);
 
+/// <summary>The unit price a new line would get if left blank — same rule as on save
+/// (SALE_PRICE, else GRN_WEIGHTED_AVG for the warehouse, else FIFO_AVG).</summary>
+public sealed record SalesSuggestedPriceDto(int ItemId, int WarehouseId, decimal UnitPrice, string PriceSource);
+
+/// <summary>Issuable stock for one item at one warehouse (on-hand less on-hold), for New Sale's
+/// per-line shortage warning. <c>IsStocked</c> false = non-stock item, never limited.</summary>
+public sealed record SalesStockAvailabilityDto(int ItemId, int WarehouseId, bool IsStocked, decimal Available);
+
 public sealed class CreateSalesInvoiceLineRequest
 {
     [Required] public int ItemId { get; set; }

Backend/ERPCore/Infra/Persistence/Configurations/ItemImageConfiguration.cs

@@ -0,0 +1,25 @@
+using ERPCore.Domain.Entities;
+using Microsoft.EntityFrameworkCore;
+using Microsoft.EntityFrameworkCore.Metadata.Builders;
+
+namespace ERPCore.Infra.Persistence.Configurations;
+
+public sealed class ItemImageConfiguration : IEntityTypeConfiguration<ItemImage>
+{
+    public void Configure(EntityTypeBuilder<ItemImage> builder)
+    {
+        builder.ToTable("item_images");
+        builder.HasKey(i => i.ItemImageId);
+
+        builder.Property(i => i.OriginalFileName).IsRequired().HasMaxLength(260);
+        builder.Property(i => i.StoredFileName).IsRequired().HasMaxLength(260);
+        builder.Property(i => i.RelativePath).IsRequired().HasMaxLength(500);
+        builder.Property(i => i.ContentType).IsRequired().HasMaxLength(200);
+        builder.Property(i => i.UploadedAt).IsRequired();
+
+        builder.HasOne(i => i.Item).WithMany()
+            .HasForeignKey(i => i.ItemId).OnDelete(DeleteBehavior.Cascade);
+
+        builder.HasIndex(i => new { i.ItemId, i.SortOrder });
+    }
+}

Backend/ERPCore/Infra/Persistence/Configurations/ProductConfigConfiguration.cs

@@ -29,7 +29,9 @@ public sealed class ProductConfigConfiguration : IEntityTypeConfiguration<Produc
         builder.Property(c => c.SerialNumbersEnabled).IsRequired().HasDefaultValue(true);
         builder.Property(c => c.BatchListsEnabled).IsRequired().HasDefaultValue(true);
         builder.Property(c => c.WarrantyPeriodsEnabled).IsRequired().HasDefaultValue(true);
-
+        builder.Property(c => c.CustomVariantsEnabled).IsRequired().HasDefaultValue(false);
+        builder.Property(c => c.ItemImagesEnabled).IsRequired().HasDefaultValue(false);
+        builder.Property(c => c.CustomWarrantyPeriodsEnabled).IsRequired().HasDefaultValue(false);
         // PostgreSQL xmin system column as the optimistic concurrency token (ETag).
         builder.Property(c => c.RowVersion).IsRowVersion();
 

Backend/ERPCore/Infra/Persistence/Configurations/SalesConfigConfiguration.cs

@@ -0,0 +1,49 @@
+using ERPCore.Domain.Entities;
+using Microsoft.EntityFrameworkCore;
+using Microsoft.EntityFrameworkCore.Metadata.Builders;
+
+namespace ERPCore.Infra.Persistence.Configurations;
+
+/// <summary>
+/// Configures the singleton sales-configuration row. The check constraint is what makes
+/// "singleton" a database guarantee rather than a convention (mirrors BranchConfig).
+/// </summary>
+public sealed class SalesConfigConfiguration : IEntityTypeConfiguration<SalesConfig>
+{
+    public void Configure(EntityTypeBuilder<SalesConfig> builder)
+    {
+        builder.ToTable("sales_config", t =>
+            t.HasCheckConstraint("ck_sales_config_singleton", $"\"ConfigId\" = {SalesConfig.SingletonId}"));
+
+        builder.HasKey(c => c.ConfigId);
+
+        // The id is fixed, never generated — there is exactly one row, seeded by DataSeeder.
+        builder.Property(c => c.ConfigId).ValueGeneratedNever();
+
+        builder.Property(c => c.AllowCashCustomer).IsRequired().HasDefaultValue(false);
+        // Sentinel = the CLR initializer (true), so an explicit false is still written on insert
+        // instead of being swallowed by the database default.
+        builder.Property(c => c.AllowFreeItems).IsRequired().HasDefaultValue(true).HasSentinel(true);
+        builder.Property(c => c.AllowDiscounts).IsRequired().HasDefaultValue(true).HasSentinel(true);
+        builder.Property(c => c.AllowOverStockSale).IsRequired().HasDefaultValue(false);
+        builder.Property(c => c.AllowWarehouseSelection).IsRequired().HasDefaultValue(true).HasSentinel(true);
+
+        builder.HasOne(c => c.DefaultWarehouse)
+            .WithMany()
+            .HasForeignKey(c => c.DefaultWarehouseId)
+            .OnDelete(DeleteBehavior.SetNull);
+
+        // PostgreSQL xmin system column as the optimistic concurrency token (ETag).
+        builder.Property(c => c.RowVersion).IsRowVersion();
+
+        builder.HasOne(c => c.CashCustomer)
+            .WithMany()
+            .HasForeignKey(c => c.CashCustomerId)
+            .OnDelete(DeleteBehavior.SetNull);
+
+        builder.HasOne(c => c.UpdatedByUser)
+            .WithMany()
+            .HasForeignKey(c => c.UpdatedBy)
+            .OnDelete(DeleteBehavior.Restrict);
+    }
+}

Backend/ERPCore/Infra/Persistence/Configurations/WarrantyPeriodConfiguration.cs

@@ -0,0 +1,27 @@
+using ERPCore.Domain.Entities;
+using ERPCore.Domain.Enums;
+using Microsoft.EntityFrameworkCore;
+using Microsoft.EntityFrameworkCore.Metadata.Builders;
+
+namespace ERPCore.Infra.Persistence.Configurations;
+
+/// <summary>Custom warranty period master. No relationships — items store months, not a reference.</summary>
+public sealed class WarrantyPeriodConfiguration : IEntityTypeConfiguration<WarrantyPeriod>
+{
+    public void Configure(EntityTypeBuilder<WarrantyPeriod> builder)
+    {
+        builder.ToTable("warranty_periods", t =>
+            t.HasCheckConstraint("ck_warranty_periods_months", "\"Months\" BETWEEN 1 AND 600"));
+        builder.HasKey(p => p.WarrantyPeriodId);
+
+        builder.Property(p => p.Months).IsRequired();
+        builder.HasIndex(p => p.Months).IsUnique();
+
+        builder.Property(p => p.Status)
+            .HasConversion<string>().HasMaxLength(20).IsRequired()
+            .HasDefaultValue(EntityStatus.Active);
+
+        builder.Property(p => p.CreatedAt).IsRequired();
+        builder.HasIndex(p => p.Status);
+    }
+}

Backend/ERPCore/Infra/Persistence/DataSeeder.cs

@@ -46,6 +46,7 @@ public static class DataSeeder
         // dirty |= await SeedCompanyProfileAsync(db, ct);
         dirty |= await SeedProductConfigAsync(db, ct);
         dirty |= await SeedBranchConfigAsync(db, ct);
+        dirty |= await SeedSalesConfigAsync(db, ct);
         dirty |= await SeedNotificationConfigAsync(db, ct);
         dirty |= await SeedSalesMastersAsync(db, ct);
         dirty |= await SeedSalesStockAsync(db, ct);
@@ -106,7 +107,10 @@ public static class DataSeeder
             SellingPricesEnabled = true,
             SerialNumbersEnabled = true,
             BatchListsEnabled = true,
-            WarrantyPeriodsEnabled = true
+            WarrantyPeriodsEnabled = true,
+            CustomVariantsEnabled = false,
+            ItemImagesEnabled = false,
+            CustomWarrantyPeriodsEnabled = false
         });
         return true;
     }
@@ -128,6 +132,18 @@ public static class DataSeeder
         return true;
     }
 
+    /// <summary>
+    /// Ensures the singleton sales-config row exists. Starts with cash customer sales off, so
+    /// every sale needs a real customer until an admin opts in from Settings → Configuration → Sales Configuration.
+    /// </summary>
+    private static async Task<bool> SeedSalesConfigAsync(ErpDbContext db, CancellationToken ct)
+    {
+        if (await db.SalesConfig.AnyAsync(c => c.ConfigId == SalesConfig.SingletonId, ct)) return false;
+
+        db.SalesConfig.Add(new SalesConfig { ConfigId = SalesConfig.SingletonId, AllowCashCustomer = false });
+        return true;
+    }
+
     private static async Task<bool> SeedNotificationConfigAsync(ErpDbContext db, CancellationToken ct)
     {
         if (await db.NotificationConfig.AnyAsync(c => c.NotificationConfigId == NotificationConfig.SingletonId, ct)) return false;

Backend/ERPCore/Infra/Persistence/ErpDbContext.cs

@@ -35,6 +35,8 @@ public class ErpDbContext : DbContext
     public DbSet<TaxRate> TaxRates => Set<TaxRate>();
     public DbSet<Item> Items => Set<Item>();
     public DbSet<ItemReorder> ItemReorders => Set<ItemReorder>();
+    public DbSet<ItemImage> ItemImages => Set<ItemImage>();
+    public DbSet<WarrantyPeriod> WarrantyPeriods => Set<WarrantyPeriod>();
     public DbSet<Vendor> Vendors => Set<Vendor>();
     public DbSet<Warehouse> Warehouses => Set<Warehouse>();
     public DbSet<Bin> Bins => Set<Bin>();
@@ -43,6 +45,7 @@ public class ErpDbContext : DbContext
     public DbSet<ProductConfig> ProductConfig => Set<ProductConfig>();
     /// <summary>Singleton row gating whether this deployment uses branches at all.</summary>
     public DbSet<BranchConfig> BranchConfig => Set<BranchConfig>();
+    public DbSet<SalesConfig> SalesConfig => Set<SalesConfig>();
     /// <summary>Singleton row for notification delivery preferences.</summary>
     public DbSet<NotificationConfig> NotificationConfig => Set<NotificationConfig>();
     public DbSet<NotificationConfigModule> NotificationConfigModules => Set<NotificationConfigModule>();

Backend/ERPCore/Migrations/20260929131905_AddSalesConfig.cs

@@ -0,0 +1,61 @@
+using System;
+using Microsoft.EntityFrameworkCore.Migrations;
+
+#nullable disable
+
+namespace ERPCore.Migrations
+{
+    /// <inheritdoc />
+    public partial class AddSalesConfig : Migration
+    {
+        /// <inheritdoc />
+        protected override void Up(MigrationBuilder migrationBuilder)
+        {
+            migrationBuilder.CreateTable(
+                name: "sales_config",
+                columns: table => new
+                {
+                    ConfigId = table.Column<int>(type: "integer", nullable: false),
+                    AllowCashCustomer = table.Column<bool>(type: "boolean", nullable: false, defaultValue: false),
+                    CashCustomerId = table.Column<int>(type: "integer", nullable: true),
+                    UpdatedAt = table.Column<DateTime>(type: "timestamp with time zone", nullable: true),
+                    UpdatedBy = table.Column<int>(type: "integer", nullable: true),
+                    xmin = table.Column<uint>(type: "xid", rowVersion: true, nullable: false)
+                },
+                constraints: table =>
+                {
+                    table.PrimaryKey("PK_sales_config", x => x.ConfigId);
+                    table.CheckConstraint("ck_sales_config_singleton", "\"ConfigId\" = 1");
+                    table.ForeignKey(
+                        name: "FK_sales_config_customers_CashCustomerId",
+                        column: x => x.CashCustomerId,
+                        principalTable: "customers",
+                        principalColumn: "CustomerId",
+                        onDelete: ReferentialAction.SetNull);
+                    table.ForeignKey(
+                        name: "FK_sales_config_users_UpdatedBy",
+                        column: x => x.UpdatedBy,
+                        principalTable: "users",
+                        principalColumn: "UserId",
+                        onDelete: ReferentialAction.Restrict);
+                });
+
+            migrationBuilder.CreateIndex(
+                name: "IX_sales_config_CashCustomerId",
+                table: "sales_config",
+                column: "CashCustomerId");
+
+            migrationBuilder.CreateIndex(
+                name: "IX_sales_config_UpdatedBy",
+                table: "sales_config",
+                column: "UpdatedBy");
+        }
+
+        /// <inheritdoc />
+        protected override void Down(MigrationBuilder migrationBuilder)
+        {
+            migrationBuilder.DropTable(
+                name: "sales_config");
+        }
+    }
+}

Backend/ERPCore/Migrations/20260930043658_AddSalesConfigAllowFreeItems.cs

@@ -0,0 +1,29 @@
+using Microsoft.EntityFrameworkCore.Migrations;
+
+#nullable disable
+
+namespace ERPCore.Migrations
+{
+    /// <inheritdoc />
+    public partial class AddSalesConfigAllowFreeItems : Migration
+    {
+        /// <inheritdoc />
+        protected override void Up(MigrationBuilder migrationBuilder)
+        {
+            migrationBuilder.AddColumn<bool>(
+                name: "AllowFreeItems",
+                table: "sales_config",
+                type: "boolean",
+                nullable: false,
+                defaultValue: true);
+        }
+
+        /// <inheritdoc />
+        protected override void Down(MigrationBuilder migrationBuilder)
+        {
+            migrationBuilder.DropColumn(
+                name: "AllowFreeItems",
+                table: "sales_config");
+        }
+    }
+}

Backend/ERPCore/Migrations/20260930044903_AddSalesConfigAllowOverStockSale.cs

@@ -0,0 +1,29 @@
+using Microsoft.EntityFrameworkCore.Migrations;
+
+#nullable disable
+
+namespace ERPCore.Migrations
+{
+    /// <inheritdoc />
+    public partial class AddSalesConfigAllowOverStockSale : Migration
+    {
+        /// <inheritdoc />
+        protected override void Up(MigrationBuilder migrationBuilder)
+        {
+            migrationBuilder.AddColumn<bool>(
+                name: "AllowOverStockSale",
+                table: "sales_config",
+                type: "boolean",
+                nullable: false,
+                defaultValue: false);
+        }
+
+        /// <inheritdoc />
+        protected override void Down(MigrationBuilder migrationBuilder)
+        {
+            migrationBuilder.DropColumn(
+                name: "AllowOverStockSale",
+                table: "sales_config");
+        }
+    }
+}

Backend/ERPCore/Migrations/20260930050220_AddSalesConfigWarehouseSelection.cs

@@ -0,0 +1,60 @@
+using Microsoft.EntityFrameworkCore.Migrations;
+
+#nullable disable
+
+namespace ERPCore.Migrations
+{
+    /// <inheritdoc />
+    public partial class AddSalesConfigWarehouseSelection : Migration
+    {
+        /// <inheritdoc />
+        protected override void Up(MigrationBuilder migrationBuilder)
+        {
+            migrationBuilder.AddColumn<bool>(
+                name: "AllowWarehouseSelection",
+                table: "sales_config",
+                type: "boolean",
+                nullable: false,
+                defaultValue: true);
+
+            migrationBuilder.AddColumn<int>(
+                name: "DefaultWarehouseId",
+                table: "sales_config",
+                type: "integer",
+                nullable: true);
+
+            migrationBuilder.CreateIndex(
+                name: "IX_sales_config_DefaultWarehouseId",
+                table: "sales_config",
+                column: "DefaultWarehouseId");
+
+            migrationBuilder.AddForeignKey(
+                name: "FK_sales_config_warehouses_DefaultWarehouseId",
+                table: "sales_config",
+                column: "DefaultWarehouseId",
+                principalTable: "warehouses",
+                principalColumn: "WarehouseId",
+                onDelete: ReferentialAction.SetNull);
+        }
+
+        /// <inheritdoc />
+        protected override void Down(MigrationBuilder migrationBuilder)
+        {
+            migrationBuilder.DropForeignKey(
+                name: "FK_sales_config_warehouses_DefaultWarehouseId",
+                table: "sales_config");
+
+            migrationBuilder.DropIndex(
+                name: "IX_sales_config_DefaultWarehouseId",
+                table: "sales_config");
+
+            migrationBuilder.DropColumn(
+                name: "AllowWarehouseSelection",
+                table: "sales_config");
+
+            migrationBuilder.DropColumn(
+                name: "DefaultWarehouseId",
+                table: "sales_config");
+        }
+    }
+}

Backend/ERPCore/Migrations/20260930062500_AddProductConfigCustomVariants.cs

@@ -0,0 +1,29 @@
+using Microsoft.EntityFrameworkCore.Migrations;
+
+#nullable disable
+
+namespace ERPCore.Migrations
+{
+    /// <inheritdoc />
+    public partial class AddProductConfigCustomVariants : Migration
+    {
+        /// <inheritdoc />
+        protected override void Up(MigrationBuilder migrationBuilder)
+        {
+            migrationBuilder.AddColumn<bool>(
+                name: "CustomVariantsEnabled",
+                table: "product_config",
+                type: "boolean",
+                nullable: false,
+                defaultValue: false);
+        }
+
+        /// <inheritdoc />
+        protected override void Down(MigrationBuilder migrationBuilder)
+        {
+            migrationBuilder.DropColumn(
+                name: "CustomVariantsEnabled",
+                table: "product_config");
+        }
+    }
+}

Backend/ERPCore/Migrations/20260930063644_AddItemImages.cs

@@ -0,0 +1,66 @@
+using System;
+using Microsoft.EntityFrameworkCore.Migrations;
+using Npgsql.EntityFrameworkCore.PostgreSQL.Metadata;
+
+#nullable disable
+
+namespace ERPCore.Migrations
+{
+    /// <inheritdoc />
+    public partial class AddItemImages : Migration
+    {
+        /// <inheritdoc />
+        protected override void Up(MigrationBuilder migrationBuilder)
+        {
+            migrationBuilder.AddColumn<bool>(
+                name: "ItemImagesEnabled",
+                table: "product_config",
+                type: "boolean",
+                nullable: false,
+                defaultValue: false);
+
+            migrationBuilder.CreateTable(
+                name: "item_images",
+                columns: table => new
+                {
+                    ItemImageId = table.Column<int>(type: "integer", nullable: false)
+                        .Annotation("Npgsql:ValueGenerationStrategy", NpgsqlValueGenerationStrategy.IdentityByDefaultColumn),
+                    ItemId = table.Column<int>(type: "integer", nullable: false),
+                    OriginalFileName = table.Column<string>(type: "character varying(260)", maxLength: 260, nullable: false),
+                    StoredFileName = table.Column<string>(type: "character varying(260)", maxLength: 260, nullable: false),
+                    RelativePath = table.Column<string>(type: "character varying(500)", maxLength: 500, nullable: false),
+                    ContentType = table.Column<string>(type: "character varying(200)", maxLength: 200, nullable: false),
+                    SizeBytes = table.Column<long>(type: "bigint", nullable: false),
+                    SortOrder = table.Column<int>(type: "integer", nullable: false),
+                    UploadedBy = table.Column<int>(type: "integer", nullable: false),
+                    UploadedAt = table.Column<DateTime>(type: "timestamp with time zone", nullable: false)
+                },
+                constraints: table =>
+                {
+                    table.PrimaryKey("PK_item_images", x => x.ItemImageId);
+                    table.ForeignKey(
+                        name: "FK_item_images_items_ItemId",
+                        column: x => x.ItemId,
+                        principalTable: "items",
+                        principalColumn: "ItemId",
+                        onDelete: ReferentialAction.Cascade);
+                });
+
+            migrationBuilder.CreateIndex(
+                name: "IX_item_images_ItemId_SortOrder",
+                table: "item_images",
+                columns: new[] { "ItemId", "SortOrder" });
+        }
+
+        /// <inheritdoc />
+        protected override void Down(MigrationBuilder migrationBuilder)
+        {
+            migrationBuilder.DropTable(
+                name: "item_images");
+
+            migrationBuilder.DropColumn(
+                name: "ItemImagesEnabled",
+                table: "product_config");
+        }
+    }
+}

Backend/ERPCore/Migrations/20260930065738_AddCustomWarrantyPeriods.cs

@@ -0,0 +1,41 @@
+using System.Collections.Generic;
+using Microsoft.EntityFrameworkCore.Migrations;
+
+#nullable disable
+
+namespace ERPCore.Migrations
+{
+    /// <inheritdoc />
+    public partial class AddCustomWarrantyPeriods : Migration
+    {
+        /// <inheritdoc />
+        protected override void Up(MigrationBuilder migrationBuilder)
+        {
+            migrationBuilder.AddColumn<List<int>>(
+                name: "CustomWarrantyPeriodMonths",
+                table: "product_config",
+                type: "integer[]",
+                nullable: false,
+                defaultValueSql: "'{}'::integer[]");
+
+            migrationBuilder.AddColumn<bool>(
+                name: "CustomWarrantyPeriodsEnabled",
+                table: "product_config",
+                type: "boolean",
+                nullable: false,
+                defaultValue: false);
+        }
+
+        /// <inheritdoc />
+        protected override void Down(MigrationBuilder migrationBuilder)
+        {
+            migrationBuilder.DropColumn(
+                name: "CustomWarrantyPeriodMonths",
+                table: "product_config");
+
+            migrationBuilder.DropColumn(
+                name: "CustomWarrantyPeriodsEnabled",
+                table: "product_config");
+        }
+    }
+}

Backend/ERPCore/Migrations/20260930071621_MoveCustomWarrantyPeriodsToMaster.cs

@@ -0,0 +1,80 @@
+using System;
+using System.Collections.Generic;
+using Microsoft.EntityFrameworkCore.Migrations;
+using Npgsql.EntityFrameworkCore.PostgreSQL.Metadata;
+
+#nullable disable
+
+namespace ERPCore.Migrations
+{
+    /// <inheritdoc />
+    public partial class MoveCustomWarrantyPeriodsToMaster : Migration
+    {
+        /// <inheritdoc />
+        protected override void Up(MigrationBuilder migrationBuilder)
+        {
+            migrationBuilder.CreateTable(
+                name: "warranty_periods",
+                columns: table => new
+                {
+                    WarrantyPeriodId = table.Column<int>(type: "integer", nullable: false)
+                        .Annotation("Npgsql:ValueGenerationStrategy", NpgsqlValueGenerationStrategy.IdentityByDefaultColumn),
+                    Months = table.Column<int>(type: "integer", nullable: false),
+                    Status = table.Column<string>(type: "character varying(20)", maxLength: 20, nullable: false, defaultValue: "Active"),
+                    CreatedAt = table.Column<DateTime>(type: "timestamp with time zone", nullable: false),
+                    UpdatedAt = table.Column<DateTime>(type: "timestamp with time zone", nullable: true)
+                },
+                constraints: table =>
+                {
+                    table.PrimaryKey("PK_warranty_periods", x => x.WarrantyPeriodId);
+                    table.CheckConstraint("ck_warranty_periods_months", "\"Months\" BETWEEN 1 AND 600");
+                });
+
+            migrationBuilder.CreateIndex(
+                name: "IX_warranty_periods_Months",
+                table: "warranty_periods",
+                column: "Months",
+                unique: true);
+
+            migrationBuilder.CreateIndex(
+                name: "IX_warranty_periods_Status",
+                table: "warranty_periods",
+                column: "Status");
+
+            // Carry over any periods already saved on the config (hand-added — EF would have
+            // dropped the column first and lost them). Out-of-range values are skipped rather
+            // than failing the check constraint.
+            migrationBuilder.Sql("""
+                INSERT INTO warranty_periods ("Months", "Status", "CreatedAt")
+                SELECT DISTINCT m, 'Active', now()
+                FROM product_config, unnest("CustomWarrantyPeriodMonths") AS m
+                WHERE m BETWEEN 1 AND 600
+                ON CONFLICT ("Months") DO NOTHING;
+                """);
+
+            migrationBuilder.DropColumn(
+                name: "CustomWarrantyPeriodMonths",
+                table: "product_config");
+        }
+
+        /// <inheritdoc />
+        protected override void Down(MigrationBuilder migrationBuilder)
+        {
+            migrationBuilder.AddColumn<List<int>>(
+                name: "CustomWarrantyPeriodMonths",
+                table: "product_config",
+                type: "integer[]",
+                nullable: false,
+                defaultValueSql: "'{}'::integer[]");
+
+            migrationBuilder.Sql("""
+                UPDATE product_config SET "CustomWarrantyPeriodMonths" = COALESCE(
+                    (SELECT array_agg("Months" ORDER BY "Months") FROM warranty_periods WHERE "Status" = 'Active'),
+                    '{}'::integer[]);
+                """);
+
+            migrationBuilder.DropTable(
+                name: "warranty_periods");
+        }
+    }
+}

Backend/ERPCore/Migrations/20260930094023_AddSalesConfigAllowDiscounts.cs

@@ -0,0 +1,29 @@
+using Microsoft.EntityFrameworkCore.Migrations;
+
+#nullable disable
+
+namespace ERPCore.Migrations
+{
+    /// <inheritdoc />
+    public partial class AddSalesConfigAllowDiscounts : Migration
+    {
+        /// <inheritdoc />
+        protected override void Up(MigrationBuilder migrationBuilder)
+        {
+            migrationBuilder.AddColumn<bool>(
+                name: "AllowDiscounts",
+                table: "sales_config",
+                type: "boolean",
+                nullable: false,
+                defaultValue: true);
+        }
+
+        /// <inheritdoc />
+        protected override void Down(MigrationBuilder migrationBuilder)
+        {
+            migrationBuilder.DropColumn(
+                name: "AllowDiscounts",
+                table: "sales_config");
+        }
+    }
+}

Backend/ERPCore/Migrations/ErpDbContextModelSnapshot.cs

@@ -1831,6 +1831,56 @@ namespace ERPCore.Migrations
                     b.ToTable("items", (string)null);
                 });
 
+            modelBuilder.Entity("ERPCore.Domain.Entities.ItemImage", b =>
+                {
+                    b.Property<int>("ItemImageId")
+                        .ValueGeneratedOnAdd()
+                        .HasColumnType("integer");
+
+                    NpgsqlPropertyBuilderExtensions.UseIdentityByDefaultColumn(b.Property<int>("ItemImageId"));
+
+                    b.Property<string>("ContentType")
+                        .IsRequired()
+                        .HasMaxLength(200)
+                        .HasColumnType("character varying(200)");
+
+                    b.Property<int>("ItemId")
+                        .HasColumnType("integer");
+
+                    b.Property<string>("OriginalFileName")
+                        .IsRequired()
+                        .HasMaxLength(260)
+                        .HasColumnType("character varying(260)");
+
+                    b.Property<string>("RelativePath")
+                        .IsRequired()
+                        .HasMaxLength(500)
+                        .HasColumnType("character varying(500)");
+
+                    b.Property<long>("SizeBytes")
+                        .HasColumnType("bigint");
+
+                    b.Property<int>("SortOrder")
+                        .HasColumnType("integer");
+
+                    b.Property<string>("StoredFileName")
+                        .IsRequired()
+                        .HasMaxLength(260)
+                        .HasColumnType("character varying(260)");
+
+                    b.Property<DateTime>("UploadedAt")
+                        .HasColumnType("timestamp with time zone");
+
+                    b.Property<int>("UploadedBy")
+                        .HasColumnType("integer");
+
+                    b.HasKey("ItemImageId");
+
+                    b.HasIndex("ItemId", "SortOrder");
+
+                    b.ToTable("item_images", (string)null);
+                });
+
             modelBuilder.Entity("ERPCore.Domain.Entities.ItemReorder", b =>
                 {
                     b.Property<int>("ReorderId")
@@ -3252,6 +3302,21 @@ namespace ERPCore.Migrations
                         .HasColumnType("boolean")
                         .HasDefaultValue(true);
 
+                    b.Property<bool>("CustomVariantsEnabled")
+                        .ValueGeneratedOnAdd()
+                        .HasColumnType("boolean")
+                        .HasDefaultValue(false);
+
+                    b.Property<bool>("CustomWarrantyPeriodsEnabled")
+                        .ValueGeneratedOnAdd()
+                        .HasColumnType("boolean")
+                        .HasDefaultValue(false);
+
+                    b.Property<bool>("ItemImagesEnabled")
+                        .ValueGeneratedOnAdd()
+                        .HasColumnType("boolean")
+                        .HasDefaultValue(false);
+
                     b.Property<bool>("ItemTypesEnabled")
                         .ValueGeneratedOnAdd()
                         .HasColumnType("boolean")
@@ -4337,6 +4402,68 @@ namespace ERPCore.Migrations
                     b.ToTable("hr_salary_components", (string)null);
                 });
 
+            modelBuilder.Entity("ERPCore.Domain.Entities.SalesConfig", b =>
+                {
+                    b.Property<int>("ConfigId")
+                        .HasColumnType("integer");
+
+                    b.Property<bool>("AllowCashCustomer")
+                        .ValueGeneratedOnAdd()
+                        .HasColumnType("boolean")
+                        .HasDefaultValue(false);
+
+                    b.Property<bool>("AllowDiscounts")
+                        .ValueGeneratedOnAdd()
+                        .HasColumnType("boolean")
+                        .HasDefaultValue(true);
+
+                    b.Property<bool>("AllowFreeItems")
+                        .ValueGeneratedOnAdd()
+                        .HasColumnType("boolean")
+                        .HasDefaultValue(true);
+
+                    b.Property<bool>("AllowOverStockSale")
+                        .ValueGeneratedOnAdd()
+                        .HasColumnType("boolean")
+                        .HasDefaultValue(false);
+
+                    b.Property<bool>("AllowWarehouseSelection")
+                        .ValueGeneratedOnAdd()
+                        .HasColumnType("boolean")
+                        .HasDefaultValue(true);
+
+                    b.Property<int?>("CashCustomerId")
+                        .HasColumnType("integer");
+
+                    b.Property<int?>("DefaultWarehouseId")
+                        .HasColumnType("integer");
+
+                    b.Property<uint>("RowVersion")
+                        .IsConcurrencyToken()
+                        .ValueGeneratedOnAddOrUpdate()
+                        .HasColumnType("xid")
+                        .HasColumnName("xmin");
+
+                    b.Property<DateTime?>("UpdatedAt")
+                        .HasColumnType("timestamp with time zone");
+
+                    b.Property<int?>("UpdatedBy")
+                        .HasColumnType("integer");
+
+                    b.HasKey("ConfigId");
+
+                    b.HasIndex("CashCustomerId");
+
+                    b.HasIndex("DefaultWarehouseId");
+
+                    b.HasIndex("UpdatedBy");
+
+                    b.ToTable("sales_config", null, t =>
+                        {
+                            t.HasCheckConstraint("ck_sales_config_singleton", "\"ConfigId\" = 1");
+                        });
+                });
+
             modelBuilder.Entity("ERPCore.Domain.Entities.SalesDayEnd", b =>
                 {
                     b.Property<int>("SalesDayEndId")
@@ -6593,6 +6720,43 @@ namespace ERPCore.Migrations
                     b.ToTable("warehouses", (string)null);
                 });
 
+            modelBuilder.Entity("ERPCore.Domain.Entities.WarrantyPeriod", b =>
+                {
+                    b.Property<int>("WarrantyPeriodId")
+                        .ValueGeneratedOnAdd()
+                        .HasColumnType("integer");
+
+                    NpgsqlPropertyBuilderExtensions.UseIdentityByDefaultColumn(b.Property<int>("WarrantyPeriodId"));
+
+                    b.Property<DateTime>("CreatedAt")
+                        .HasColumnType("timestamp with time zone");
+
+                    b.Property<int>("Months")
+                        .HasColumnType("integer");
+
+                    b.Property<string>("Status")
+                        .IsRequired()
+                        .ValueGeneratedOnAdd()
+                        .HasMaxLength(20)
+                        .HasColumnType("character varying(20)")
+                        .HasDefaultValue("Active");
+
+                    b.Property<DateTime?>("UpdatedAt")
+                        .HasColumnType("timestamp with time zone");
+
+                    b.HasKey("WarrantyPeriodId");
+
+                    b.HasIndex("Months")
+                        .IsUnique();
+
+                    b.HasIndex("Status");
+
+                    b.ToTable("warranty_periods", null, t =>
+                        {
+                            t.HasCheckConstraint("ck_warranty_periods_months", "\"Months\" BETWEEN 1 AND 600");
+                        });
+                });
+
             modelBuilder.Entity("ERPCore.Domain.Entities.WorkShift", b =>
                 {
                     b.Property<int>("WorkShiftId")
@@ -7145,6 +7309,17 @@ namespace ERPCore.Migrations
                     b.Navigation("TaxRate");
                 });
 
+            modelBuilder.Entity("ERPCore.Domain.Entities.ItemImage", b =>
+                {
+                    b.HasOne("ERPCore.Domain.Entities.Item", "Item")
+                        .WithMany()
+                        .HasForeignKey("ItemId")
+                        .OnDelete(DeleteBehavior.Cascade)
+                        .IsRequired();
+
+                    b.Navigation("Item");
+                });
+
             modelBuilder.Entity("ERPCore.Domain.Entities.ItemReorder", b =>
                 {
                     b.HasOne("ERPCore.Domain.Entities.Item", "Item")
@@ -7835,6 +8010,30 @@ namespace ERPCore.Migrations
                     b.Navigation("Uom");
                 });
 
+            modelBuilder.Entity("ERPCore.Domain.Entities.SalesConfig", b =>
+                {
+                    b.HasOne("ERPCore.Domain.Entities.Customer", "CashCustomer")
+                        .WithMany()
+                        .HasForeignKey("CashCustomerId")
+                        .OnDelete(DeleteBehavior.SetNull);
+
+                    b.HasOne("ERPCore.Domain.Entities.Warehouse", "DefaultWarehouse")
+                        .WithMany()
+                        .HasForeignKey("DefaultWarehouseId")
+                        .OnDelete(DeleteBehavior.SetNull);
+
+                    b.HasOne("ERPCore.Domain.Entities.User", "UpdatedByUser")
+                        .WithMany()
+                        .HasForeignKey("UpdatedBy")
+                        .OnDelete(DeleteBehavior.Restrict);
+
+                    b.Navigation("CashCustomer");
+
+                    b.Navigation("DefaultWarehouse");
+
+                    b.Navigation("UpdatedByUser");
+                });
+
             modelBuilder.Entity("ERPCore.Domain.Entities.SalesDayEnd", b =>
                 {
                     b.HasOne("ERPCore.Domain.Entities.User", "CashierUser")

Backend/ERPCore/Program.cs

@@ -87,6 +87,8 @@ builder.Services.AddScoped(typeof(IRepository<>), typeof(Repository<>));
 // Master-data services (docs/11 §2)
 builder.Services.AddScoped<ICustomerService, CustomerService>();
 builder.Services.AddScoped<IItemService, ItemService>();
+builder.Services.AddScoped<IItemImageService, ItemImageService>();
+builder.Services.AddScoped<IWarrantyPeriodService, WarrantyPeriodService>();
 builder.Services.AddScoped<IUomService, UomService>();
 builder.Services.AddScoped<ICategoryService, CategoryService>();
 builder.Services.AddScoped<IBrandService, BrandService>();
@@ -95,6 +97,7 @@ builder.Services.AddScoped<IItemTypeService, ItemTypeService>();
 //builder.Services.AddScoped<ICompanyProfileService, CompanyProfileService>();
 builder.Services.AddScoped<IProductConfigService, ProductConfigService>();
 builder.Services.AddScoped<IBranchConfigService, BranchConfigService>();
+builder.Services.AddScoped<ISalesConfigService, SalesConfigService>();
 builder.Services.AddScoped<IBranchAccessService, BranchAccessService>();
 builder.Services.AddSingleton<INotificationModuleCatalog, NotificationModuleCatalog>();
 builder.Services.AddScoped<INotificationConfigService, NotificationConfigService>();

Backend/ERPCore/Services/Hrm/EmployeeService.cs

@@ -285,9 +285,18 @@ public sealed class EmployeeService : IEmployeeService
         }
         catch (DbUpdateException)
         {
+            // Every save a user makes writes an AuditLog row against their UserId, so almost any
+            // real user is still referenced by history and can't be hard-deleted. The login is
+            // still permanently removed: the row is kept only as a tombstone so historical
+            // "created by" references stay intact — credentials/contact scrubbed, role revoked,
+            // and hidden from Settings > Users. The AuthHex identity is purged below as usual.
+            // Update() flips the entity back from Deleted, or the next save would retry the delete.
+            _users.Update(user);
+            user.Username = User.DeletedUsernamePrefix + user.UserId;
+            user.Email = null;
+            user.RoleId = null;
             user.Status = EntityStatus.Inactive;
             await _uow.SaveChangesAsync(ct);
-            return new EmployeeDeleteResultDto(UserAccountDeleted: false, UserAccountDeactivated: true, AuthHexIdentityPurged: false);
         }
 
         // The local User row is gone, but AuthHex's own duplicate check (CanRegisterUser) has no

Backend/ERPCore/Services/Interfaces/IFifoCostingService.cs

@@ -24,10 +24,16 @@ public interface IFifoCostingService
     /// stock. Throws <c>STOCK_NEGATIVE_BLOCKED</c> if issuable stock is insufficient,
     /// <c>EXPIRED_BATCH_BLOCKED</c>/<c>ONHOLD_NOT_ISSUABLE</c> for an explicit batch
     /// that is expired/held. Returns the consumed segments (for cost-preserving moves
-    /// and ledger costing). Must run inside a UoW transaction.
+    /// and ledger costing). Must run inside a UoW transaction. Any shortfall layers left by an
+    /// earlier over-stock sale are settled against issuable stock first.
     /// </summary>
+    /// <param name="allowShortfall">
+    /// Sales only (Sales Configuration "Allow selling beyond stock"): instead of throwing, the
+    /// quantity stock can't cover is recorded as a negative layer at the last known unit cost.
+    /// </param>
     Task<IReadOnlyList<ConsumedSegment>> ConsumeAsync(
-        int itemId, int warehouseId, int? batchId, decimal qtyBase, CancellationToken ct = default);
+        int itemId, int warehouseId, int? batchId, decimal qtyBase, CancellationToken ct = default,
+        bool allowShortfall = false);
 
     /// <summary>
     /// Append an immutable ledger entry. Value defaults to <c>round(qtyBase × unitCost, 4)</c>.

Backend/ERPCore/Services/Interfaces/IItemImageService.cs

@@ -0,0 +1,16 @@
+using ERPCore.Dtos.Items;
+
+namespace ERPCore.Services.Interfaces;
+
+/// <summary>Item photos — upload gated by <c>ProductConfig.ItemImagesEnabled</c>; reads never gated.</summary>
+public interface IItemImageService
+{
+    Task<List<ItemImageDto>> ListAsync(int itemId, CancellationToken ct = default);
+
+    Task<ItemImageDto> UploadAsync(
+        int itemId, Stream content, string fileName, string contentType, int actorUserId, CancellationToken ct = default);
+
+    Task<(Stream Content, string ContentType)> OpenAsync(int itemId, int itemImageId, CancellationToken ct = default);
+
+    Task DeleteAsync(int itemId, int itemImageId, CancellationToken ct = default);
+}

Backend/ERPCore/Services/Interfaces/IItemService.cs

@@ -19,6 +19,7 @@ public interface IItemService
     /// last-purchase and trailing-30-day sales aggregates for the Items list page.</summary>
     Task<PagedResponse<ItemOverviewDto>> GetOverviewAsync(
         PageQuery query, EntityStatus? status, int? categoryId, int? subCategoryId, int? brandId,
+        TrackingMode? trackingMode, StockNature? stockNature, ItemStockFilter? stock,
         CancellationToken ct = default);
 
     Task<ETagged<ItemDetailDto>?> GetAsync(int itemId, CancellationToken ct = default);

Backend/ERPCore/Services/Interfaces/IProductConfigService.cs

@@ -9,5 +9,4 @@ public interface IProductConfigService
     Task<ETagged<ProductConfigDto>> GetAsync(CancellationToken ct = default);
 
     Task<ETagged<ProductConfigDto>> UpdateAsync(
-        UpdateProductConfigRequest request, uint expectedRowVersion, CancellationToken ct = default);
-}
+        UpdateProductConfigRequest request, uint expectedRowVersion, CancellationToken ct = default);}

Backend/ERPCore/Services/Interfaces/ISalesConfigService.cs

@@ -0,0 +1,14 @@
+using ERPCore.Common.Http;
+using ERPCore.Dtos.Config;
+
+namespace ERPCore.Services.Interfaces;
+
+/// <summary>Sales configuration business logic. Singleton.</summary>
+public interface ISalesConfigService
+{
+    Task<ETagged<SalesConfigDto>> GetAsync(CancellationToken ct = default);
+
+    /// <summary>Switching <c>AllowCashCustomer</c> on creates the cash customer on first use.</summary>
+    Task<ETagged<SalesConfigDto>> UpdateAsync(
+        UpdateSalesConfigRequest request, uint expectedRowVersion, CancellationToken ct = default);
+}

Backend/ERPCore/Services/Interfaces/ISalesDomainService.cs

@@ -12,6 +12,19 @@ public interface ISalesDomainService
         bool requireCashierUser,
         CancellationToken ct = default);
 
+    /// <summary>Sales Configuration "Allow free items" — gates free qty on sales invoice lines.</summary>
+    Task<bool> AreFreeItemsAllowedAsync(CancellationToken ct = default);
+
+    /// <summary>Sales Configuration "Allow discounts" — gates line discounts on sales invoice lines.</summary>
+    Task<bool> AreDiscountsAllowedAsync(CancellationToken ct = default);
+
+    /// <summary>Sales Configuration "Allow selling beyond stock" — lets sales posting drive on-hand negative.</summary>
+    Task<bool> IsOverStockSaleAllowedAsync(CancellationToken ct = default);
+
+    /// <summary>Sales Configuration default sales warehouse: when one is saved, every sales invoice
+    /// must use it. Null only when none is saved and "Allow warehouse selection" is on.</summary>
+    Task<int?> GetForcedSalesWarehouseIdAsync(CancellationToken ct = default);
+
     Task ValidateSalesLineAsync(
         int headerWarehouseId,
         int lineItemId,

Backend/ERPCore/Services/Interfaces/IWarrantyPeriodService.cs

@@ -0,0 +1,16 @@
+using ERPCore.Domain.Enums;
+using ERPCore.Dtos.Items;
+
+namespace ERPCore.Services.Interfaces;
+
+/// <summary>Custom warranty period master. Never hard-deleted (FR-MD-08).</summary>
+public interface IWarrantyPeriodService
+{
+    Task<List<WarrantyPeriodDto>> ListAsync(EntityStatus? status, CancellationToken ct = default);
+
+    /// <summary>1–600 months, not a default length. Re-adding an inactive length reactivates it;
+    /// an active duplicate is a 409.</summary>
+    Task<WarrantyPeriodDto> CreateAsync(int months, CancellationToken ct = default);
+
+    Task SetStatusAsync(int warrantyPeriodId, EntityStatus status, CancellationToken ct = default);
+}

Backend/ERPCore/Services/ItemImageService.cs

@@ -0,0 +1,131 @@
+using ERPCore.Domain.Entities;
+using ERPCore.Dtos.Items;
+using ERPCore.Infra.Storage;
+using ERPCore.Infra.UoW;
+using ERPCore.Repositories.Interfaces;
+using ERPCore.Services.Interfaces;
+using ERPCore.System.Errors;
+using Microsoft.EntityFrameworkCore;
+
+namespace ERPCore.Services;
+
+/// <summary>
+/// Item photo service. Same upload rules as staff documents — extension allowlist, declared
+/// content-type cross-check and a size cap, server-authoritative — narrowed to web image
+/// formats, plus a per-item count cap. Uploads are refused with <c>CONFIG_DISABLED</c> while
+/// <c>ProductConfig.ItemImagesEnabled</c> is off; listing, viewing and deleting stay open so
+/// images added earlier remain manageable.
+/// </summary>
+public sealed class ItemImageService : IItemImageService
+{
+    public const int MaxImagesPerItem = 10;
+    public const long MaxSizeBytes = 5 * 1024 * 1024;
+
+    private static readonly Dictionary<string, string> AllowedExtensionContentTypes = new(StringComparer.OrdinalIgnoreCase)
+    {
+        [".jpg"] = "image/jpeg",
+        [".jpeg"] = "image/jpeg",
+        [".png"] = "image/png",
+        [".webp"] = "image/webp"
+    };
+
+    private readonly IRepository<ItemImage> _images;
+    private readonly IRepository<Item> _items;
+    private readonly IProductConfigService _config;
+    private readonly IFileStorageService _storage;
+    private readonly IUnitOfWork _uow;
+
+    public ItemImageService(
+        IRepository<ItemImage> images, IRepository<Item> items, IProductConfigService config,
+        IFileStorageService storage, IUnitOfWork uow)
+    {
+        _images = images;
+        _items = items;
+        _config = config;
+        _storage = storage;
+        _uow = uow;
+    }
+
+    public async Task<List<ItemImageDto>> ListAsync(int itemId, CancellationToken ct = default)
+    {
+        await EnsureItemExistsAsync(itemId, ct);
+        return await _images.Query().AsNoTracking()
+            .Where(i => i.ItemId == itemId)
+            .OrderBy(i => i.SortOrder).ThenBy(i => i.ItemImageId)
+            .Select(i => new ItemImageDto(i.ItemImageId, i.ItemId, i.OriginalFileName, i.ContentType, i.SizeBytes, i.SortOrder, i.UploadedAt))
+            .ToListAsync(ct);
+    }
+
+    public async Task<ItemImageDto> UploadAsync(
+        int itemId, Stream content, string fileName, string contentType, int actorUserId, CancellationToken ct = default)
+    {
+        if (!(await _config.GetAsync(ct)).Value.ItemImagesEnabled)
+            throw new DomainException(ErrorCodes.ConfigDisabled,
+                "Item images are disabled in the product configuration.", 422);
+
+        await EnsureItemExistsAsync(itemId, ct);
+
+        var extension = Path.GetExtension(fileName);
+        if (!AllowedExtensionContentTypes.TryGetValue(extension, out var expectedContentType)
+            || !string.Equals(expectedContentType, contentType, StringComparison.OrdinalIgnoreCase))
+            throw new DomainException(ErrorCodes.FileTypeNotAllowed,
+                $"File type '{extension}'/'{contentType}' is not allowed. Use JPG, PNG or WebP.", 422);
+
+        if (content.Length > MaxSizeBytes)
+            throw new DomainException(ErrorCodes.FileTooLarge,
+                $"Image exceeds the maximum allowed size of {MaxSizeBytes / (1024 * 1024)} MB.", 413);
+
+        var existing = await _images.Query().Where(i => i.ItemId == itemId).Select(i => i.SortOrder).ToListAsync(ct);
+        if (existing.Count >= MaxImagesPerItem)
+            throw new DomainException(ErrorCodes.Validation,
+                $"An item can have at most {MaxImagesPerItem} images.", 422);
+
+        var (storedFileName, relativePath, sizeBytes) = await _storage.SaveAsync(content, fileName, contentType, ct);
+
+        var image = new ItemImage
+        {
+            ItemId = itemId,
+            OriginalFileName = Path.GetFileName(fileName),
+            StoredFileName = storedFileName,
+            RelativePath = relativePath,
+            ContentType = expectedContentType,
+            SizeBytes = sizeBytes,
+            SortOrder = existing.Count == 0 ? 0 : existing.Max() + 1,
+            UploadedBy = actorUserId,
+            UploadedAt = DateTime.UtcNow
+        };
+
+        await _images.AddAsync(image, ct);
+        await _uow.SaveChangesAsync(ct);
+
+        return new ItemImageDto(image.ItemImageId, image.ItemId, image.OriginalFileName, image.ContentType,
+            image.SizeBytes, image.SortOrder, image.UploadedAt);
+    }
+
+    public async Task<(Stream Content, string ContentType)> OpenAsync(int itemId, int itemImageId, CancellationToken ct = default)
+    {
+        var image = await _images.Query().AsNoTracking()
+            .FirstOrDefaultAsync(i => i.ItemImageId == itemImageId && i.ItemId == itemId, ct)
+            ?? throw new NotFoundException($"Image {itemImageId} was not found for item {itemId}.");
+
+        return (await _storage.OpenReadAsync(image.RelativePath, ct), image.ContentType);
+    }
+
+    public async Task DeleteAsync(int itemId, int itemImageId, CancellationToken ct = default)
+    {
+        var image = await _images.Query()
+            .FirstOrDefaultAsync(i => i.ItemImageId == itemImageId && i.ItemId == itemId, ct)
+            ?? throw new NotFoundException($"Image {itemImageId} was not found for item {itemId}.");
+
+        _images.Remove(image);
+        await _uow.SaveChangesAsync(ct);
+        // File removed only after the row is gone, so a failed save never orphans a row.
+        await _storage.DeleteAsync(image.RelativePath, ct);
+    }
+
+    private async Task EnsureItemExistsAsync(int itemId, CancellationToken ct)
+    {
+        if (!await _items.Query().AnyAsync(i => i.ItemId == itemId, ct))
+            throw new NotFoundException($"Item {itemId} was not found.");
+    }
+}

Backend/ERPCore/Services/ItemService.cs

@@ -114,6 +114,7 @@ public sealed class ItemService : IItemService
 
     public async Task<PagedResponse<ItemOverviewDto>> GetOverviewAsync(
         PageQuery query, EntityStatus? status, int? categoryId, int? subCategoryId, int? brandId,
+        TrackingMode? trackingMode, StockNature? stockNature, ItemStockFilter? stock,
         CancellationToken ct = default)
     {
         var q = _items.Query().AsNoTracking();
@@ -127,6 +128,24 @@ public sealed class ItemService : IItemService
         if (categoryId is not null) q = q.Where(i => i.CategoryId == categoryId);
         if (subCategoryId is not null) q = q.Where(i => i.SubCategoryId == subCategoryId);
         if (brandId is not null) q = q.Where(i => i.BrandId == brandId);
+        if (trackingMode is not null) q = q.Where(i => i.TrackingMode == trackingMode);
+        if (stockNature is not null) q = q.Where(i => i.StockNature == stockNature);
+        // Stock-state filters run as subqueries before paging, so totals and pages stay correct.
+        var layers = _stockLayers.Query();
+        switch (stock)
+        {
+            case ItemStockFilter.InStock:
+                q = q.Where(i => layers.Where(l => l.ItemId == i.ItemId).Sum(l => (decimal?)l.QtyRemaining) > 0);
+                break;
+            case ItemStockFilter.OutOfStock:
+                q = q.Where(i => (layers.Where(l => l.ItemId == i.ItemId).Sum(l => (decimal?)l.QtyRemaining) ?? 0) <= 0);
+                break;
+            case ItemStockFilter.LowStock:
+                q = q.Where(i => i.ReorderSettings.Any(rs =>
+                    (layers.Where(l => l.ItemId == rs.ItemId && l.WarehouseId == rs.WarehouseId)
+                        .Sum(l => (decimal?)l.QtyRemaining) ?? 0) <= rs.ReorderPoint));
+                break;
+        }
 
         var total = await q.CountAsync(ct);
         var page = await q.OrderBy(i => i.Sku)
@@ -135,16 +154,16 @@ public sealed class ItemService : IItemService
             .ToListAsync(ct);
         var itemIds = page.Select(i => i.ItemId).ToList();
 
-        // Current FIFO stock value/qty — every open layer, every warehouse.
+        // Current FIFO stock value/qty — every open layer (negative = sold beyond stock), every warehouse.
         var stockByItem = await _stockLayers.Query().AsNoTracking()
-            .Where(l => itemIds.Contains(l.ItemId) && l.QtyRemaining > 0)
+            .Where(l => itemIds.Contains(l.ItemId) && l.QtyRemaining != 0)
             .GroupBy(l => l.ItemId)
             .Select(g => new { ItemId = g.Key, Qty = g.Sum(x => x.QtyRemaining), Value = g.Sum(x => x.QtyRemaining * x.UnitCost) })
             .ToDictionaryAsync(x => x.ItemId, ct);
 
         // On-hand per (item, warehouse), to compare against each item's reorder settings.
         var onHandByItemWarehouse = (await _stockLayers.Query().AsNoTracking()
-            .Where(l => itemIds.Contains(l.ItemId) && l.QtyRemaining > 0)
+            .Where(l => itemIds.Contains(l.ItemId) && l.QtyRemaining != 0)
             .GroupBy(l => new { l.ItemId, l.WarehouseId })
             .Select(g => new { g.Key.ItemId, g.Key.WarehouseId, Qty = g.Sum(x => x.QtyRemaining) })
             .ToListAsync(ct))
@@ -215,7 +234,7 @@ public sealed class ItemService : IItemService
 
         ItemContent.ValidatePair(request.ContentQty, request.ContentUnit);
         var (contentBaseQty, contentBaseUnit) = ItemContent.Normalize(request.ContentQty, request.ContentUnit);
-        var warrantyPeriodMonths = ValidateWarrantyPeriod(request.Warranty, request.WarrantyPeriodMonths);
+        var warrantyPeriodMonths = ValidateWarrantyPeriod(request.Warranty, request.WarrantyPeriodMonths, config, null);
 
         var item = new Item
         {
@@ -292,7 +311,8 @@ public sealed class ItemService : IItemService
 
         ItemContent.ValidatePair(request.ContentQty, request.ContentUnit);
         var (contentBaseQty, contentBaseUnit) = ItemContent.Normalize(request.ContentQty, request.ContentUnit);
-        var warrantyPeriodMonths = ValidateWarrantyPeriod(request.Warranty, request.WarrantyPeriodMonths);
+        var warrantyPeriodMonths = ValidateWarrantyPeriod(
+            request.Warranty, request.WarrantyPeriodMonths, config, item.WarrantyPeriodMonths);
 
         item.Sku = request.Sku.Trim();
         item.Name = request.Name.Trim();
@@ -506,18 +526,33 @@ public sealed class ItemService : IItemService
     }
 
     /// <summary>
-    /// A warranty-tracked item must declare a coverage period (one of
-    /// <see cref="WarrantyPeriods.AllowedMonths"/>); a non-warranty item carries none —
-    /// any value sent for one is silently dropped rather than trusted from the client.
+    /// A warranty-tracked item must declare a coverage period. With custom periods off it must
+    /// be one of <see cref="WarrantyPeriods.AllowedMonths"/>; with them on, any length of
+    /// 1–<see cref="WarrantyPeriodService.MaxMonths"/> months — the Warranty Periods master is
+    /// just the shared presets, and an item may also carry a length of its own entered on the
+    /// item form (never added to the master). On update the item's <paramref name="currentMonths"/>
+    /// is also accepted, so switching the feature off never blocks editing an item that already
+    /// uses a custom length. A non-warranty item carries none — any value sent for one is
+    /// silently dropped rather than trusted from the client.
     /// </summary>
-    private static int? ValidateWarrantyPeriod(Warranty warranty, int? warrantyPeriodMonths)
+    private static int? ValidateWarrantyPeriod(
+        Warranty warranty, int? warrantyPeriodMonths, ProductConfigDto config, int? currentMonths)
     {
         if (warranty != Warranty.Warranty) return null;
 
-        if (warrantyPeriodMonths is null || !WarrantyPeriods.AllowedMonths.Contains(warrantyPeriodMonths.Value))
+        var valid = warrantyPeriodMonths is not null
+            && (warrantyPeriodMonths == currentMonths
+                || (config.CustomWarrantyPeriodsEnabled
+                    ? warrantyPeriodMonths is >= 1 and <= WarrantyPeriodService.MaxMonths
+                    : WarrantyPeriods.AllowedMonths.Contains(warrantyPeriodMonths.Value)));
+
+        if (!valid)
             throw new DomainException(
                 ErrorCodes.Validation,
-                $"Warranty period must be one of {string.Join(", ", WarrantyPeriods.AllowedMonths)} months.", 422);
+                config.CustomWarrantyPeriodsEnabled
+                    ? $"Warranty period must be between 1 and {WarrantyPeriodService.MaxMonths} months."
+                    : $"Warranty period must be one of {string.Join(", ", WarrantyPeriods.AllowedMonths)} months.",
+                422);
 
         return warrantyPeriodMonths;
     }

Backend/ERPCore/Services/ProductConfigService.cs

@@ -55,6 +55,13 @@ public sealed class ProductConfigService : IProductConfigService
         config.SerialNumbersEnabled = request.SerialNumbersEnabled!.Value;
         config.BatchListsEnabled = request.BatchListsEnabled!.Value;
         config.WarrantyPeriodsEnabled = request.WarrantyPeriodsEnabled!.Value;
+        // Custom variants live in the item-variants section - switching product variants
+        // off switches this off too, so it can never be left on by itself.
+        config.CustomVariantsEnabled = config.ItemTypesEnabled && request.CustomVariantsEnabled!.Value;
+        config.ItemImagesEnabled = request.ItemImagesEnabled!.Value;
+        // Custom warranty periods depend on warranty periods - switching the parent off
+        // switches this off too, so it can never be left on by itself.
+        config.CustomWarrantyPeriodsEnabled = config.WarrantyPeriodsEnabled && request.CustomWarrantyPeriodsEnabled!.Value;
         config.UpdatedAt = DateTime.UtcNow;
         config.UpdatedBy = _currentUser.AuditUserId;
 
@@ -73,5 +80,7 @@ public sealed class ProductConfigService : IProductConfigService
     private static ProductConfigDto Map(ProductConfig c) => new(
         c.SubcategoriesEnabled, c.BrandsEnabled, c.ItemTypesEnabled,
         c.SellingPricesEnabled, c.SerialNumbersEnabled, c.BatchListsEnabled, c.WarrantyPeriodsEnabled,
+        c.CustomVariantsEnabled, c.ItemImagesEnabled,
+        c.CustomWarrantyPeriodsEnabled,
         c.UpdatedAt, c.UpdatedBy);
 }

Backend/ERPCore/Services/SalesConfigService.cs

@@ -0,0 +1,120 @@
+using ERPCore.Common.Http;
+using ERPCore.Domain.Entities;
+using ERPCore.Domain.Enums;
+using ERPCore.Dtos.Config;
+using ERPCore.Infra.Auth;
+using ERPCore.Infra.UoW;
+using ERPCore.Repositories.Interfaces;
+using ERPCore.Services.Interfaces;
+using ERPCore.System.Errors;
+using Microsoft.EntityFrameworkCore;
+
+namespace ERPCore.Services;
+
+/// <summary>
+/// Sales configuration service over the singleton row seeded by DataSeeder. Also owns the
+/// generic "Cash Customer" record — created the first time cash sales are allowed.
+/// </summary>
+public sealed class SalesConfigService : ISalesConfigService
+{
+    private const string CashCustomerCode = "CUST-CASH";
+    private const string CashCustomerName = "Cash Customer";
+
+    private readonly IRepository<SalesConfig> _config;
+    private readonly IRepository<Customer> _customers;
+    private readonly IRepository<Warehouse> _warehouses;
+    private readonly IBranchConfigService _branchConfig;
+    private readonly ICurrentUser _currentUser;
+    private readonly IUnitOfWork _uow;
+
+    public SalesConfigService(
+        IRepository<SalesConfig> config, IRepository<Customer> customers, IRepository<Warehouse> warehouses,
+        IBranchConfigService branchConfig, ICurrentUser currentUser, IUnitOfWork uow)
+    {
+        _config = config;
+        _customers = customers;
+        _warehouses = warehouses;
+        _branchConfig = branchConfig;
+        _currentUser = currentUser;
+        _uow = uow;
+    }
+
+    public async Task<ETagged<SalesConfigDto>> GetAsync(CancellationToken ct = default)
+    {
+        var config = await _config.Query().AsNoTracking().Include(c => c.CashCustomer).Include(c => c.DefaultWarehouse)
+            .FirstOrDefaultAsync(c => c.ConfigId == SalesConfig.SingletonId, ct)
+            ?? throw new NotFoundException("Sales configuration has not been seeded.");
+
+        return new ETagged<SalesConfigDto>(Map(config), config.RowVersion);
+    }
+
+    public async Task<ETagged<SalesConfigDto>> UpdateAsync(
+        UpdateSalesConfigRequest request, uint expectedRowVersion, CancellationToken ct = default)
+    {
+        var config = await _config.GetByIdAsync(SalesConfig.SingletonId, ct)
+            ?? throw new NotFoundException("Sales configuration has not been seeded.");
+
+        if (config.RowVersion != expectedRowVersion)
+            throw new DomainException(ErrorCodes.ConcurrencyConflict, "The configuration was modified by another request.", 412);
+
+        // Validated before anything is applied — ResolveCashCustomerIdAsync below saves, so a
+        // later throw would otherwise leave the row half-updated.
+        var allowWarehouseSelection = request.AllowWarehouseSelection!.Value;
+        if (!allowWarehouseSelection && request.DefaultWarehouseId is null)
+            throw new DomainException(ErrorCodes.Validation, "Pick a default sales warehouse before turning warehouse selection off.", 422);
+        if (request.DefaultWarehouseId is int defaultWarehouseId
+            && !await _warehouses.Query().AnyAsync(w => w.WarehouseId == defaultWarehouseId, ct))
+            throw new NotFoundException($"Warehouse {defaultWarehouseId} was not found.");
+
+        config.AllowCashCustomer =request.AllowCashCustomer!.Value;
+        if (config.AllowCashCustomer && config.CashCustomerId is null)
+            config.CashCustomerId = await ResolveCashCustomerIdAsync(ct);
+        config.AllowFreeItems = request.AllowFreeItems!.Value;
+        config.AllowDiscounts = request.AllowDiscounts!.Value;
+        config.AllowOverStockSale = request.AllowOverStockSale!.Value;
+        config.AllowWarehouseSelection = allowWarehouseSelection;
+        config.DefaultWarehouseId = request.DefaultWarehouseId;
+        config.UpdatedAt = DateTime.UtcNow;
+        config.UpdatedBy = _currentUser.AuditUserId;
+
+        try
+        {
+            await _uow.SaveChangesAsync(ct);
+        }
+        catch (DbUpdateConcurrencyException)
+        {
+            throw new DomainException(ErrorCodes.ConcurrencyConflict, "The configuration was modified by another request.", 412);
+        }
+
+        return await GetAsync(ct);
+    }
+
+    // Reuses an existing CUST-CASH row (e.g. one left behind by a config row reset) before
+    // creating a new one on the deployment's default branch.
+    private async Task<int> ResolveCashCustomerIdAsync(CancellationToken ct)
+    {
+        var existingId = await _customers.Query().AsNoTracking()
+            .Where(c => c.CustomerCode == CashCustomerCode).Select(c => c.CustomerId).FirstOrDefaultAsync(ct);
+        if (existingId != 0) return existingId;
+
+        var customer = new Customer
+        {
+            CustomerCode = CashCustomerCode,
+            CustomerType = CustomerType.WalkIn,
+            Name = CashCustomerName,
+            DisplayName = CashCustomerName,
+            CreditLimit = 0m,
+            CreditDays = 0,
+            BranchId = await _branchConfig.ResolveDefaultBranchIdAsync(ct),
+            Status = EntityStatus.Active,
+            CreatedAt = DateTime.UtcNow
+        };
+        await _customers.AddAsync(customer, ct);
+        await _uow.SaveChangesAsync(ct);
+        return customer.CustomerId;
+    }
+
+    private static SalesConfigDto Map(SalesConfig c) => new(
+        c.AllowCashCustomer, c.CashCustomerId, c.CashCustomer?.DisplayName ?? c.CashCustomer?.Name, c.AllowFreeItems, c.AllowDiscounts, c.AllowOverStockSale,
+        c.AllowWarehouseSelection, c.DefaultWarehouseId, c.DefaultWarehouse?.Name, c.UpdatedAt, c.UpdatedBy);
+}

Backend/ERPCore/Services/SalesDomainService.cs

@@ -15,6 +15,7 @@ public sealed class SalesDomainService : ISalesDomainService
     private readonly IRepository<Item> _items;
     private readonly IRepository<TaxRate> _taxRates;
     private readonly ISalesPricingService _pricing;
+    private readonly IRepository<SalesConfig> _salesConfig;
 
     public SalesDomainService(
         IRepository<Customer> customers,
@@ -22,7 +23,8 @@ public sealed class SalesDomainService : ISalesDomainService
         IRepository<User> users,
         IRepository<Item> items,
         IRepository<TaxRate> taxRates,
-        ISalesPricingService pricing)
+        ISalesPricingService pricing,
+        IRepository<SalesConfig> salesConfig)
     {
         _customers = customers;
         _warehouses = warehouses;
@@ -30,12 +32,20 @@ public sealed class SalesDomainService : ISalesDomainService
         _items = items;
         _taxRates = taxRates;
         _pricing = pricing;
+        _salesConfig = salesConfig;
     }
 
     public async Task ValidateSalesHeaderAsync(int customerId, int warehouseId, int? cashierUserId, bool requireCashierUser, CancellationToken ct = default)
     {
         if (!await _customers.Query().AnyAsync(x => x.CustomerId == customerId, ct))
             throw new NotFoundException($"Customer {customerId} was not found.");
+        // The generic cash customer is only usable while Sales Configuration allows it.
+        var cashConfig = await _salesConfig.Query().AsNoTracking()
+            .Where(c => c.ConfigId == SalesConfig.SingletonId)
+            .Select(c => new { c.AllowCashCustomer, c.CashCustomerId })
+            .FirstOrDefaultAsync(ct);
+        if (cashConfig is { AllowCashCustomer: false } && cashConfig.CashCustomerId == customerId)
+            throw new DomainException(ErrorCodes.Validation, "Cash customer sales are turned off in Sales Configuration. Select a customer.", 422);
         if (!await _warehouses.Query().AnyAsync(x => x.WarehouseId == warehouseId, ct))
             throw new NotFoundException($"Warehouse {warehouseId} was not found.");
         if (requireCashierUser)
@@ -47,6 +57,40 @@ public sealed class SalesDomainService : ISalesDomainService
         }
     }
 
+    // A missing config row means the option predates it — free items stay allowed.
+    public async Task<bool> AreFreeItemsAllowedAsync(CancellationToken ct = default) =>
+        await _salesConfig.Query().AsNoTracking()
+            .Where(c => c.ConfigId == SalesConfig.SingletonId)
+            .Select(c => (bool?)c.AllowFreeItems)
+            .FirstOrDefaultAsync(ct) ?? true;
+
+    // A missing config row means the option predates it — discounts stay allowed.
+    public async Task<bool> AreDiscountsAllowedAsync(CancellationToken ct = default) =>
+        await _salesConfig.Query().AsNoTracking()
+            .Where(c => c.ConfigId == SalesConfig.SingletonId)
+            .Select(c => (bool?)c.AllowDiscounts)
+            .FirstOrDefaultAsync(ct) ?? true;
+
+    public async Task<int?> GetForcedSalesWarehouseIdAsync(CancellationToken ct = default)
+    {
+        var config = await _salesConfig.Query().AsNoTracking()
+            .Where(c => c.ConfigId == SalesConfig.SingletonId)
+            .Select(c => new { c.AllowWarehouseSelection, c.DefaultWarehouseId })
+            .FirstOrDefaultAsync(ct);
+        if (config is null) return null;
+        // A saved default sales warehouse always wins — sales use only that warehouse.
+        if (config.DefaultWarehouseId is int defaultWarehouseId) return defaultWarehouseId;
+        if (config.AllowWarehouseSelection) return null;
+        // The FK is SetNull on delete, so the default can disappear after it was configured.
+        throw new DomainException(ErrorCodes.Validation, "Warehouse selection is turned off in Sales Configuration but no default sales warehouse is set.", 422);
+    }
+
+    public async Task<bool> IsOverStockSaleAllowedAsync(CancellationToken ct = default) =>
+        await _salesConfig.Query().AsNoTracking()
+            .Where(c => c.ConfigId == SalesConfig.SingletonId)
+            .Select(c => c.AllowOverStockSale)
+            .FirstOrDefaultAsync(ct);
+
     public async Task ValidateSalesLineAsync(
         int headerWarehouseId, int lineItemId, int lineWarehouseId, decimal qty, decimal freeQty, int? parentLineId, CancellationToken ct = default)
     {

Backend/ERPCore/Services/SalesInvoiceService.cs

@@ -86,6 +86,7 @@ public sealed class SalesInvoiceService : ISalesInvoiceService
 
     public async Task<ETagged<SalesInvoiceDto>> CreateAsync(CreateSalesInvoiceRequest request, CancellationToken ct = default)
     {
+        request.WarehouseId = await ApplyForcedWarehouseAsync(request.WarehouseId, request.Lines, ct);
         await _sales.ValidateSalesHeaderAsync(request.CustomerId, request.WarehouseId, null, false, ct);
         var branchId = await _branchConfig.ResolveBranchIdAsync(request.BranchId, ct);
 
@@ -122,6 +123,7 @@ public sealed class SalesInvoiceService : ISalesInvoiceService
     {
         var invoice = await _workflow.LoadEditableInvoiceAsync(salesInvoiceId, expectedRowVersion, ct);
 
+        request.WarehouseId = await ApplyForcedWarehouseAsync(request.WarehouseId, request.Lines, ct);
         await _sales.ValidateSalesHeaderAsync(request.CustomerId, request.WarehouseId, null, false, ct);
         invoice.CustomerId = request.CustomerId;
         invoice.WarehouseId = request.WarehouseId;
@@ -157,9 +159,22 @@ public sealed class SalesInvoiceService : ISalesInvoiceService
         return _mapping.MapInvoice(invoice);
     }
 
+    // Sales Configuration "Allow warehouse selection" off: whatever the client sent, the header
+    // and every line use the configured default sales warehouse.
+    private async Task<int> ApplyForcedWarehouseAsync(int requestedWarehouseId, List<CreateSalesInvoiceLineRequest> lines, CancellationToken ct)
+    {
+        if (await _sales.GetForcedSalesWarehouseIdAsync(ct) is not int forced) return requestedWarehouseId;
+        foreach (var line in lines) line.WarehouseId = forced;
+        return forced;
+    }
+
     private async Task<List<SalesInvoiceLine>> BuildLinesAsync(int headerWarehouseId, List<CreateSalesInvoiceLineRequest> requests, CancellationToken ct)
     {
         var lines = new List<SalesInvoiceLine>();
+        if (requests.Any(r => r.FreeQty > 0m || r.IsFreeIssue) && !await _sales.AreFreeItemsAllowedAsync(ct))
+            throw new DomainException(ErrorCodes.Validation, "Free items are turned off in Sales Configuration.", 422);
+        if (requests.Any(r => r.DiscountPct > 0m || r.DiscountAmount > 0m || r.DiscountValue > 0m) && !await _sales.AreDiscountsAllowedAsync(ct))
+            throw new DomainException(ErrorCodes.Validation, "Discounts are turned off in Sales Configuration.", 422);
         foreach (var r in requests)
         {
             var item = await _items.Query().AsNoTracking().FirstAsync(x => x.ItemId == r.ItemId, ct);

Backend/ERPCore/Services/SalesPostingService.cs

@@ -93,7 +93,8 @@ public sealed class SalesPostingService : ISalesPostingService
                 requestedQty, available, requestedQty - available, line.IsFreeIssue));
         }
 
-        return new SalesInvoicePostingCheckDto(invoice.SalesInvoiceId, invoice.InvoiceNo, invoice.Status, issues.Count == 0, issues);
+        return new SalesInvoicePostingCheckDto(invoice.SalesInvoiceId, invoice.InvoiceNo, invoice.Status,
+            issues.Count == 0 || await _sales.IsOverStockSaleAllowedAsync(ct), issues);
     }
 
     public async Task<SalesSlipPostingCheckDto> CheckSlipAsync(int salesSlipId, CancellationToken ct = default)
@@ -124,7 +125,8 @@ public sealed class SalesPostingService : ISalesPostingService
                 requestedQty, available, requestedQty - available, line.IsFreeIssue));
         }
 
-        return new SalesSlipPostingCheckDto(slip.SalesSlipId, slip.SlipNo, slip.Status, issues.Count == 0, issues);
+        return new SalesSlipPostingCheckDto(slip.SalesSlipId, slip.SlipNo, slip.Status,
+            issues.Count == 0 || await _sales.IsOverStockSaleAllowedAsync(ct), issues);
     }
 
     public async Task<BundleSalePostingCheckDto> CheckBundleAsync(int bundleSaleId, CancellationToken ct = default)
@@ -151,7 +153,8 @@ public sealed class SalesPostingService : ISalesPostingService
                 line.BundleSaleLineId, line.ItemId, item.Sku, item.Name, line.WarehouseId, line.Qty, available, line.Qty - available));
         }
 
-        return new BundleSalePostingCheckDto(bundle.BundleSaleId, bundle.BundleNo, bundle.Status, issues.Count == 0, issues);
+        return new BundleSalePostingCheckDto(bundle.BundleSaleId, bundle.BundleNo, bundle.Status,
+            issues.Count == 0 || await _sales.IsOverStockSaleAllowedAsync(ct), issues);
     }
 
     public Task PostInvoiceAsync(int salesInvoiceId, CancellationToken ct = default)
@@ -260,6 +263,10 @@ public sealed class SalesPostingService : ISalesPostingService
         if (!string.Equals(statusValue, "Draft", StringComparison.Ordinal))
             throw new ConflictException(ensureDraftMessage(doc));
 
+        // Sales Configuration "Allow selling beyond stock": a short line posts anyway and drives
+        // on-hand negative instead of failing with STOCK_NEGATIVE_BLOCKED.
+        var allowShortfall = await _sales.IsOverStockSaleAllowedAsync(ct);
+
         await _uow.ExecuteInTransactionAsync(async token =>
         {
             var totalCogs = 0m;
@@ -271,7 +278,7 @@ public sealed class SalesPostingService : ISalesPostingService
 
                 // Line quantities are already a count of the item's base UOM — sales documents
                 // carry no unit of their own — so this is the quantity FIFO consumes verbatim.
-                var consumed = await _fifo.ConsumeAsync(line.ItemId, line.WarehouseId, line.BatchId, line.Qty, token);
+                var consumed = await _fifo.ConsumeAsync(line.ItemId, line.WarehouseId, line.BatchId, line.Qty, token, allowShortfall);
                 var cost = consumed.Count == 0 ? 0m : consumed.Sum(x => x.Qty * x.UnitCost) / consumed.Sum(x => x.Qty);
                 totalCogs += cost * line.Qty;
                 await _fifo.PostLedgerAsync(line.ItemId, line.WarehouseId, null, line.BatchId, line.SerialId, _currentUser.AuditUserId,

Backend/ERPCore/Services/Stock/FifoCostingService.cs

@@ -63,9 +63,11 @@ public sealed class FifoCostingService : IFifoCostingService
     }
 
     public async Task<IReadOnlyList<ConsumedSegment>> ConsumeAsync(
-        int itemId, int warehouseId, int? batchId, decimal qtyBase, CancellationToken ct = default)
+        int itemId, int warehouseId, int? batchId, decimal qtyBase, CancellationToken ct = default,
+        bool allowShortfall = false)
     {
-        var today = DateOnly.FromDateTime(DateTime.UtcNow);
+        var now = DateTime.UtcNow;
+        var today = DateOnly.FromDateTime(now);
 
         if (batchId is not null)
         {
@@ -76,27 +78,43 @@ public sealed class FifoCostingService : IFifoCostingService
                     $"Batch {batchId} expired on {expiry:yyyy-MM-dd} and cannot be issued.", 409);
         }
 
-        // Row-lock the issuable open layers oldest-first (SELECT … FOR UPDATE, NFR-02).
-        // Excludes on-hold and rejected (grn line) and expired-batch stock — rejected stock
-        // sits quarantined until a Purchase Return consumes it directly (see
-        // PurchaseReturnService), never through this general-issue path. No LINQ is
-        // composed on top of the raw SQL so the FOR UPDATE reaches the database intact.
-        // {batchId}::bigint casts give Npgsql an explicit type for the (possibly null)
-        // parameter — without it a null batch filter fails with 42P18.
-        var layers = await _db.StockLayers
+        // Row-lock the issuable open layers oldest-first (SELECT … FOR UPDATE, NFR-02), plus any
+        // shortfall (negative) layers left by an over-stock sale. Excludes on-hold and rejected
+        // (grn line) and expired-batch stock — rejected stock sits quarantined until a Purchase
+        // Return consumes it directly (see PurchaseReturnService), never through this
+        // general-issue path. No LINQ is composed on top of the raw SQL so the FOR UPDATE
+        // reaches the database intact.
+        var locked = await _db.StockLayers
             .FromSqlInterpolated($"""
                 SELECT * FROM stock_layers sl
-                WHERE sl."ItemId" = {itemId} AND sl."WarehouseId" = {warehouseId} AND sl."QtyRemaining" > 0
-                  AND ({batchId}::bigint IS NULL OR sl."BatchId" = {batchId}::bigint)
-                  AND NOT EXISTS (SELECT 1 FROM grn_lines gl WHERE gl."GrnLineId" = sl."GrnLineId" AND gl."HoldStatus" IN ('OnHold', 'Rejected'))
-                  AND NOT EXISTS (SELECT 1 FROM batches b WHERE b."BatchId" = sl."BatchId" AND b."ExpiryDate" < {today})
+                WHERE sl."ItemId" = {itemId} AND sl."WarehouseId" = {warehouseId}
+                  AND (sl."QtyRemaining" < 0 OR (sl."QtyRemaining" > 0
+                    AND NOT EXISTS (SELECT 1 FROM grn_lines gl WHERE gl."GrnLineId" = sl."GrnLineId" AND gl."HoldStatus" IN ('OnHold', 'Rejected'))
+                    AND NOT EXISTS (SELECT 1 FROM batches b WHERE b."BatchId" = sl."BatchId" AND b."ExpiryDate" < {today})))
                 ORDER BY sl."ReceiptDate", sl."LayerId"
                 FOR UPDATE
                 """)
             .ToListAsync(ct);
 
+        // Stock sold before it arrived is owed first: net shortfall layers off against issuable
+        // stock (oldest-first) before anything new is issued, so it can't be sold twice. The
+        // sale already posted its ledger Out, so settling writes no ledger entry of its own.
+        var owed = locked.Where(l => l.QtyRemaining < 0).ToList();
+        var open = locked.Where(l => l.QtyRemaining > 0).ToList();
+        foreach (var shortfall in owed)
+        {
+            foreach (var layer in open)
+            {
+                if (shortfall.QtyRemaining >= 0) break;
+                var settle = Math.Min(-shortfall.QtyRemaining, layer.QtyRemaining);
+                layer.QtyRemaining -= settle;
+                shortfall.QtyRemaining += settle;
+            }
+        }
+
+        var layers = open.Where(l => l.QtyRemaining > 0 && (batchId == null || l.BatchId == batchId)).ToList();
         var available = layers.Sum(l => l.QtyRemaining);
-        if (available < qtyBase)
+        if (available < qtyBase && !allowShortfall)
         {
             var heldExists = await _db.StockLayers.AsNoTracking().AnyAsync(l =>
                 l.ItemId == itemId && l.WarehouseId == warehouseId && l.QtyRemaining > 0
@@ -121,9 +139,40 @@ public sealed class FifoCostingService : IFifoCostingService
             segments.Add(new ConsumedSegment(layer.LayerId, take, layer.UnitCost));
         }
 
+        // Over-stock sale: whatever stock couldn't cover becomes a negative layer (on-hand goes
+        // below zero), costed at the item's last known unit cost — the next issue from this
+        // warehouse settles it against the stock received in the meantime (see above).
+        if (remaining > 0)
+        {
+            var unitCost = await LastKnownUnitCostAsync(itemId, warehouseId, ct);
+            var shortfall = new StockLayer
+            {
+                ItemId = itemId,
+                WarehouseId = warehouseId,
+                QtyReceived = 0m,
+                QtyRemaining = -remaining,
+                UnitCost = unitCost,
+                ReceiptDate = now
+            };
+            await _layers.AddAsync(shortfall, ct);
+            segments.Add(new ConsumedSegment(shortfall.LayerId, remaining, unitCost));
+        }
+
         return segments;
     }
 
+    // Most recent layer's cost at this warehouse, else anywhere, else 0 (never-stocked item).
+    private async Task<decimal> LastKnownUnitCostAsync(int itemId, int warehouseId, CancellationToken ct)
+    {
+        var layers = _layers.Query().AsNoTracking().Where(l => l.ItemId == itemId && l.QtyReceived > 0);
+        return await layers.Where(l => l.WarehouseId == warehouseId)
+                   .OrderByDescending(l => l.ReceiptDate).ThenByDescending(l => l.LayerId)
+                   .Select(l => (decimal?)l.UnitCost).FirstOrDefaultAsync(ct)
+               ?? await layers.OrderByDescending(l => l.ReceiptDate).ThenByDescending(l => l.LayerId)
+                   .Select(l => (decimal?)l.UnitCost).FirstOrDefaultAsync(ct)
+               ?? 0m;
+    }
+
     public async Task<StockLedger> PostLedgerAsync(
         int itemId, int warehouseId, int? binId, int? batchId, int? serialId, int userId,
         Direction direction, decimal qtyBase, decimal unitCost, decimal runningBalance,
@@ -195,7 +244,8 @@ public sealed class FifoCostingService : IFifoCostingService
     public async Task<StockValuationDto> GetValuationAsync(int itemId, int warehouseId, CancellationToken ct = default)
     {
         var open = await _layers.Query().AsNoTracking()
-            .Where(l => l.ItemId == itemId && l.WarehouseId == warehouseId && l.QtyRemaining > 0)
+            // Negative (over-stock sale) layers included, so valuation qty always matches on-hand.
+            .Where(l => l.ItemId == itemId && l.WarehouseId == warehouseId && l.QtyRemaining != 0)
             .OrderBy(l => l.ReceiptDate).ThenBy(l => l.LayerId)
             .Select(l => new { l.LayerId, l.QtyRemaining, l.UnitCost, l.ReceiptDate })
             .ToListAsync(ct);

Backend/ERPCore/Services/UserManagementService.cs

@@ -38,7 +38,8 @@ public sealed class UserManagementService : IUserManagementService
 
     public async Task<PagedResponse<ManagedUserDto>> ListAsync(PageQuery query, EntityStatus? status, string? roleCode, CancellationToken ct = default)
     {
-        IQueryable<User> q = _users.Query().AsNoTracking().Include(u => u.Role);
+        IQueryable<User> q = _users.Query().AsNoTracking().Include(u => u.Role)
+            .Where(u => !u.Username.StartsWith(User.DeletedUsernamePrefix));
         if (!string.IsNullOrWhiteSpace(query.Q))
         {
             var term = query.Q.Trim();

Backend/ERPCore/Services/WarrantyPeriodService.cs

@@ -0,0 +1,78 @@
+using ERPCore.Domain.Entities;
+using ERPCore.Domain.Enums;
+using ERPCore.Dtos.Items;
+using ERPCore.Infra.UoW;
+using ERPCore.Repositories.Interfaces;
+using ERPCore.Services.Interfaces;
+using ERPCore.System.Errors;
+using Microsoft.EntityFrameworkCore;
+
+namespace ERPCore.Services;
+
+/// <summary>
+/// Custom warranty period master — shared presets offered on every item's form on top of
+/// <see cref="WarrantyPeriods.AllowedMonths"/>. Not an allow-list: with custom periods on, an
+/// item may also carry a one-off length of its own. Nothing references these rows (items
+/// store months), so deactivating is always safe and there is no in-use check.
+/// </summary>
+public sealed class WarrantyPeriodService : IWarrantyPeriodService
+{
+    public const int MaxMonths = 600;
+
+    private readonly IRepository<WarrantyPeriod> _periods;
+    private readonly IUnitOfWork _uow;
+
+    public WarrantyPeriodService(IRepository<WarrantyPeriod> periods, IUnitOfWork uow)
+    {
+        _periods = periods;
+        _uow = uow;
+    }
+
+    public async Task<List<WarrantyPeriodDto>> ListAsync(EntityStatus? status, CancellationToken ct = default)
+    {
+        var q = _periods.Query().AsNoTracking();
+        if (status is not null) q = q.Where(p => p.Status == status);
+        return await q.OrderBy(p => p.Months)
+            .Select(p => new WarrantyPeriodDto(p.WarrantyPeriodId, p.Months, p.Status, p.CreatedAt, p.UpdatedAt))
+            .ToListAsync(ct);
+    }
+
+    public async Task<WarrantyPeriodDto> CreateAsync(int months, CancellationToken ct = default)
+    {
+        if (months < 1 || months > MaxMonths)
+            throw new DomainException(ErrorCodes.Validation,
+                $"A warranty period must be between 1 and {MaxMonths} months.", 422);
+        if (WarrantyPeriods.AllowedMonths.Contains(months))
+            throw new ConflictException($"{months} months is already a default warranty period.");
+
+        var existing = await _periods.Query().FirstOrDefaultAsync(p => p.Months == months, ct);
+        if (existing is not null)
+        {
+            if (existing.Status == EntityStatus.Active)
+                throw new ConflictException($"A {months}-month warranty period already exists.");
+
+            // Unique by length: re-adding a deactivated one brings it back rather than failing.
+            existing.Status = EntityStatus.Active;
+            existing.UpdatedAt = DateTime.UtcNow;
+            await _uow.SaveChangesAsync(ct);
+            return Map(existing);
+        }
+
+        var period = new WarrantyPeriod { Months = months, Status = EntityStatus.Active, CreatedAt = DateTime.UtcNow };
+        await _periods.AddAsync(period, ct);
+        await _uow.SaveChangesAsync(ct);
+        return Map(period);
+    }
+
+    public async Task SetStatusAsync(int warrantyPeriodId, EntityStatus status, CancellationToken ct = default)
+    {
+        var period = await _periods.GetByIdAsync(warrantyPeriodId, ct)
+            ?? throw new NotFoundException($"Warranty period {warrantyPeriodId} was not found.");
+
+        period.Status = status;
+        period.UpdatedAt = DateTime.UtcNow;
+        await _uow.SaveChangesAsync(ct);
+    }
+
+    private static WarrantyPeriodDto Map(WarrantyPeriod p) => new(p.WarrantyPeriodId, p.Months, p.Status, p.CreatedAt, p.UpdatedAt);
+}