Add smoke tests for UOM conversions and enhance frontend UOM management

- Implemented smoke tests for UOM directionality, ensuring conversions are one-directional and correctly validated.
- Added tests for receiving and selling items in different UOMs, verifying correct quantity handling and error responses.
- Created a UOM conversions panel in the frontend to allow users to manage UOM conversions for items.
- Introduced hooks for allowed UOMs to optimize fetching and caching of UOM data for document line forms.
- Developed utility functions for consistent UOM formatting and conversion handling across the application.

Backend/ERPCore/Dtos/Procurement/PurchaseOrderDtos.cs

@@ -5,9 +5,18 @@ namespace ERPCore.Dtos.Procurement;
 
 // Responses (docs/11 §3.3) ------------------------------------------------------
 
+/// <summary>
+/// A PO line. <paramref name="Qty"/> and <paramref name="QtyReceived"/> are in
+/// <paramref name="UomId"/> and are what the user sees; <paramref name="QtyBase"/> and
+/// <paramref name="QtyReceivedBase"/> are the item's base UOM and are what the server
+/// actually enforces — GRN over-receipt and the PO close condition both run on the base
+/// pair, because goods may legitimately be received in a different UOM from the one
+/// ordered. A client showing remaining/outstanding quantity should read the base pair.
+/// </summary>
 public sealed record PoLineDto(
     int PoLineId, int ItemId, int UomId, int WarehouseId,
-    decimal Qty, decimal UnitPrice, decimal Tax, decimal QtyReceived);
+    decimal Qty, decimal UnitPrice, decimal Tax, decimal QtyReceived,
+    decimal QtyBase = 0m, decimal QtyReceivedBase = 0m, decimal ConversionFactor = 1m);
 
 public sealed record PoTotalsDto(decimal SubTotal, decimal Tax, decimal GrandTotal, string Currency);
 

Backend/ERPCore/Dtos/Sales/BundleSaleDtos.cs

@@ -31,9 +31,10 @@ public sealed record BundleSaleTemplateSummaryDto(
     int BundleSaleTemplateId, string TemplateCode, string TemplateName, string? Description,
     EntityStatus Status, int LineCount, DateTime CreatedAt, DateTime? UpdatedAt);
 
+/// <summary>Quantities are in the item's base UOM — see <c>SalesInvoicePostingIssueDto</c>.</summary>
 public sealed record BundleSalePostingIssueDto(
     int BundleSaleLineId, int ItemId, string ItemSku, string ItemName, int WarehouseId,
-    decimal RequestedQty, decimal AvailableQty, decimal ShortQty);
+    decimal RequestedQty, decimal AvailableQty, decimal ShortQty, string BaseUomName = "");
 
 public sealed record BundleSalePostingCheckDto(
     int BundleSaleId, string BundleNo, BundleSaleStatus Status, bool CanPost,

Backend/ERPCore/Dtos/Sales/SalesInvoiceDtos.cs

@@ -24,9 +24,16 @@ public sealed record SalesInvoiceSummaryDto(
     string CustomerSnapshotName, int WarehouseId, SalesInvoiceType InvoiceType,
     SalesInvoiceStatus Status, SalesInvoiceTotalsDto Totals, DateTime CreatedAt);
 
+/// <summary>
+/// A line that cannot be posted for lack of stock. The three quantities are in the item's
+/// <b>base</b> UOM (on-hand only exists in base), which may differ from the UOM shown on the
+/// line — hence <paramref name="BaseUomName"/>: without it a line reading "2 BOX" produces
+/// an unexplained "requested 24, available 10".
+/// </summary>
 public sealed record SalesInvoicePostingIssueDto(
     int SalesInvoiceLineId, int ItemId, string ItemSku, string ItemName, int WarehouseId,
-    decimal RequestedQty, decimal AvailableQty, decimal ShortQty, bool IsFreeIssue);
+    decimal RequestedQty, decimal AvailableQty, decimal ShortQty, bool IsFreeIssue,
+    string BaseUomName = "");
 
 public sealed record SalesInvoicePostingCheckDto(
     int SalesInvoiceId, string InvoiceNo, SalesInvoiceStatus Status, bool CanPost,

Backend/ERPCore/Dtos/Sales/SalesSlipDtos.cs

@@ -23,9 +23,11 @@ public sealed record SalesSlipSummaryDto(
     string CustomerSnapshotName, int WarehouseId, SalesSlipStatus Status,
     SalesSlipTotalsDto Totals, DateTime CreatedAt);
 
+/// <summary>Quantities are in the item's base UOM — see <c>SalesInvoicePostingIssueDto</c>.</summary>
 public sealed record SalesSlipPostingIssueDto(
     int SalesSlipLineId, int ItemId, string ItemSku, string ItemName, int WarehouseId,
-    decimal RequestedQty, decimal AvailableQty, decimal ShortQty, bool IsFreeIssue);
+    decimal RequestedQty, decimal AvailableQty, decimal ShortQty, bool IsFreeIssue,
+    string BaseUomName = "");
 
 public sealed record SalesSlipPostingCheckDto(
     int SalesSlipId, string SlipNo, SalesSlipStatus Status, bool CanPost,

Backend/ERPCore/Dtos/Stock/StockDtos.cs

@@ -2,16 +2,23 @@ using ERPCore.Domain.Enums;
 
 namespace ERPCore.Dtos.Stock;
 
+// Every quantity a stock endpoint returns is in the item's base UOM — stock, layers and the
+// ledger are base-only by construction. The BaseUomId/BaseUomName pair on each of these DTOs
+// exists so a client can *label* those figures; without it every stock screen renders a bare
+// number the user has to guess the unit of. They are never a conversion instruction.
+
 /// <summary>Stock enquiry (docs/11 §5.1). available = onHand − onHold − reserved − inTransit(out).</summary>
 public sealed record StockOnHandDto(
     int ItemId, int WarehouseId, decimal OnHand, decimal Available,
-    decimal OnHold, decimal InTransit, decimal Reserved, DateTime AsOf);
+    decimal OnHold, decimal InTransit, decimal Reserved, DateTime AsOf,
+    int BaseUomId = 0, string BaseUomName = "");
 
 /// <summary>A stock-ledger row (docs/11 §5.2).</summary>
 public sealed record StockLedgerRowDto(
     int LedgerId, int ItemId, int WarehouseId, int? BinId, int? BatchId, int? SerialId,
     Direction Direction, decimal QtyBase, decimal UnitCost, decimal Value, decimal RunningBalance,
-    string SourceDocType, int SourceDocId, int UserId, DateTime CreatedAt);
+    string SourceDocType, int SourceDocId, int UserId, DateTime CreatedAt,
+    int BaseUomId = 0, string BaseUomName = "");
 
 /// <summary>An open FIFO layer in a valuation (docs/11 §5.3).</summary>
 public sealed record StockValuationLayerDto(int LayerId, decimal QtyRemaining, decimal UnitCost, decimal Value, DateTime ReceiptDate);
@@ -19,4 +26,5 @@ public sealed record StockValuationLayerDto(int LayerId, decimal QtyRemaining, d
 /// <summary>Valuation of on-hand stock from open FIFO layers (docs/11 §5.3).</summary>
 public sealed record StockValuationDto(
     int ItemId, int WarehouseId, IReadOnlyList<StockValuationLayerDto> Layers,
-    decimal TotalQty, decimal TotalValue, string Currency, string CostingMethod);
+    decimal TotalQty, decimal TotalValue, string Currency, string CostingMethod,
+    int BaseUomId = 0, string BaseUomName = "");

Backend/ERPCore/Dtos/Uoms/UomDtos.cs

@@ -9,3 +9,12 @@ public sealed class CreateUomRequest
 {
     [Required, StringLength(50)] public string Name { get; set; } = string.Empty;
 }
+
+/// <summary>
+/// A UOM an item may actually be transacted in: its base UOM (<paramref name="Factor"/> 1,
+/// <paramref name="IsBase"/> true) plus every UOM it has a conversion from. Backs both
+/// entry-time validation and <c>GET /items/{itemId}/uoms</c>, so the client can offer only
+/// units that will survive posting instead of the whole global list.
+/// </summary>
+/// <param name="Factor">Multiply a quantity in this UOM by <paramref name="Factor"/> to get base UOM.</param>
+public sealed record AllowedUomDto(int UomId, string Name, decimal Factor, bool IsBase);