completed invetory updates

Backend/ERPCore/Domain/Entities/Brand.cs

@@ -0,0 +1,21 @@
+using ERPCore.Domain.Enums;
+
+namespace ERPCore.Domain.Entities;
+
+/// <summary>
+/// Brand master (FR-MD-09). Referenced optionally by <see cref="Item.BrandId"/>.
+/// Mutable aggregate with a <see cref="RowVersion"/> ETag token. Deactivated, not
+/// deleted, when referenced (FR-MD-08). Model: docs/10-BACKEND-PHASE1.md Part C.1.
+/// </summary>
+public class Brand
+{
+    public int BrandId { get; set; }
+    public string Name { get; set; } = string.Empty;
+    public EntityStatus Status { get; set; } = EntityStatus.Active;
+
+    public DateTime CreatedAt { get; set; }
+    public DateTime? UpdatedAt { get; set; }
+
+    /// <summary>PostgreSQL xmin-backed optimistic concurrency token (ETag source).</summary>
+    public uint RowVersion { get; set; }
+}

Backend/ERPCore/Domain/Entities/Category.cs

@@ -1,15 +1,25 @@
+using ERPCore.Domain.Enums;
+
 namespace ERPCore.Domain.Entities;
 
 /// <summary>
-/// Hierarchical item category (FR-MD-04). A null <see cref="ParentId"/> denotes a
-/// root category. Model: docs/10-BACKEND-PHASE1.md Part C.1.
+/// Item category (FR-MD-04) — the top level of a two-level hierarchy. The optional level
+/// below is <see cref="SubCategory"/>; categories no longer self-nest (the former
+/// <c>parent_id</c> tree was replaced in migration #2).
+/// Mutable aggregate with a <see cref="RowVersion"/> ETag token. Deactivated, not
+/// deleted, when referenced (FR-MD-08). Model: docs/10-BACKEND-PHASE1.md Part C.1.
 /// </summary>
 public class Category
 {
     public int CategoryId { get; set; }
     public string Name { get; set; } = string.Empty;
+    public EntityStatus Status { get; set; } = EntityStatus.Active;
 
-    public int? ParentId { get; set; }
-    public Category? Parent { get; set; }
-    public ICollection<Category> Children { get; set; } = new List<Category>();
+    public DateTime CreatedAt { get; set; }
+    public DateTime? UpdatedAt { get; set; }
+
+    /// <summary>PostgreSQL xmin-backed optimistic concurrency token (ETag source).</summary>
+    public uint RowVersion { get; set; }
+
+    public ICollection<SubCategory> SubCategories { get; set; } = new List<SubCategory>();
 }

Backend/ERPCore/Domain/Entities/Item.cs

@@ -17,13 +17,20 @@ public class Item
     public int CategoryId { get; set; }
     public Category? Category { get; set; }
 
+    /// <summary>Optional second level below <see cref="CategoryId"/>; must belong to it.</summary>
+    public int? SubCategoryId { get; set; }
+    public SubCategory? SubCategory { get; set; }
+
+    public int? BrandId { get; set; }
+    public Brand? Brand { get; set; }
+
     public int BaseUomId { get; set; }
     public Uom? BaseUom { get; set; }
 
     public int? DefaultVendorId { get; set; }
     public Vendor? DefaultVendor { get; set; }
 
-    public ItemType ItemType { get; set; }
+    public StockNature StockNature { get; set; }
     public TrackingMode TrackingMode { get; set; }
     public string? TaxClass { get; set; }
     public EntityStatus Status { get; set; } = EntityStatus.Active;

Backend/ERPCore/Domain/Entities/ItemType.cs

@@ -0,0 +1,31 @@
+using ERPCore.Domain.Enums;
+
+namespace ERPCore.Domain.Entities;
+
+/// <summary>
+/// Item type master (FR-MD-10) — a selectable dimension name such as Color, Size or
+/// Material.
+/// <para>
+/// <b>Deliberately unlinked.</b> Nothing references this entity and it references
+/// nothing: there is no value table and no join to <see cref="Item"/>. Its only job is
+/// to feed the frontend's item-builder dropdown via <c>GET /item-types</c>. The chosen
+/// values (Red, S, M) are encoded by the client into the generated SKU
+/// (e.g. <c>BL-100-0003</c>) and are never stored or parsed server-side — the item list
+/// is the record of what was built. See the accepted trade-off in docs/10 Part C.9.
+/// </para>
+/// Not to be confused with <see cref="Enums.StockNature"/> (Stocked/NonStocked/Service),
+/// which is what the old <c>ItemType</c> enum became.
+/// Model: docs/10-BACKEND-PHASE1.md Part C.1.
+/// </summary>
+public class ItemType
+{
+    public int ItemTypeId { get; set; }
+    public string Name { get; set; } = string.Empty;
+    public EntityStatus Status { get; set; } = EntityStatus.Active;
+
+    public DateTime CreatedAt { get; set; }
+    public DateTime? UpdatedAt { get; set; }
+
+    /// <summary>PostgreSQL xmin-backed optimistic concurrency token (ETag source).</summary>
+    public uint RowVersion { get; set; }
+}

Backend/ERPCore/Domain/Entities/ProductConfig.cs

@@ -0,0 +1,35 @@
+namespace ERPCore.Domain.Entities;
+
+/// <summary>
+/// Product configuration (FR-MD-11) — a <b>singleton row</b> (single-tenant, docs/00-CORE §1)
+/// gating optional product master-data features.
+/// <para>
+/// <see cref="SubcategoriesEnabled"/> and <see cref="BrandsEnabled"/> are enforced
+/// server-side: an Item write carrying a subcategory/brand while the flag is off is
+/// rejected with <c>CONFIG_DISABLED</c>. <see cref="ItemTypesEnabled"/> is
+/// <b>advisory only</b> — items carry no item-type reference (see <see cref="ItemType"/>),
+/// so there is nothing on a write to reject; the frontend honours it by hiding the
+/// builder's type section. Reads are never gated, so existing data stays visible after a
+/// flag is switched off.
+/// </para>
+/// Model: docs/10-BACKEND-PHASE1.md Part C.1.
+/// </summary>
+public class ProductConfig
+{
+    /// <summary>Always 1 — the singleton row's id.</summary>
+    public const int SingletonId = 1;
+
+    public int ConfigId { get; set; }
+
+    public bool SubcategoriesEnabled { get; set; } = true;
+    public bool BrandsEnabled { get; set; } = true;
+    public bool ItemTypesEnabled { get; set; } = true;
+
+    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/SubCategory.cs

@@ -0,0 +1,26 @@
+using ERPCore.Domain.Enums;
+
+namespace ERPCore.Domain.Entities;
+
+/// <summary>
+/// Subcategory — the single optional level below <see cref="Category"/> (FR-MD-04).
+/// Replaces the former self-referencing CATEGORY.parent_id tree: the hierarchy is
+/// exactly two levels deep and cannot nest further. Referenced optionally by
+/// <see cref="Item.SubCategoryId"/>. Model: docs/10-BACKEND-PHASE1.md Part C.1.
+/// </summary>
+public class SubCategory
+{
+    public int SubCategoryId { get; set; }
+    public string Name { get; set; } = string.Empty;
+
+    public int CategoryId { get; set; }
+    public Category? Category { get; set; }
+
+    public EntityStatus Status { get; set; } = EntityStatus.Active;
+
+    public DateTime CreatedAt { get; set; }
+    public DateTime? UpdatedAt { get; set; }
+
+    /// <summary>PostgreSQL xmin-backed optimistic concurrency token (ETag source).</summary>
+    public uint RowVersion { get; set; }
+}

Backend/ERPCore/Domain/Enums/ItemType.cs

@@ -1,12 +0,0 @@
-namespace ERPCore.Domain.Enums;
-
-/// <summary>
-/// Item classification (FR-MD-01). Values match the <c>itemType</c> enum in
-/// docs/11-BACKEND-PHASE1.md §8. Stored as a string in the database.
-/// </summary>
-public enum ItemType
-{
-    Stocked,
-    NonStocked,
-    Service
-}

Backend/ERPCore/Domain/Enums/StockNature.cs

@@ -0,0 +1,14 @@
+namespace ERPCore.Domain.Enums;
+
+/// <summary>
+/// Whether an item holds stock (FR-MD-01). Values match the <c>stockNature</c> enum in
+/// docs/11-BACKEND-PHASE1.md §8. Stored as a string in the database.
+/// Renamed from <c>ItemType</c> so that name could be taken by the ItemType master
+/// entity (Color/Size/Material) — the two concepts are unrelated (docs/10 Part C.9).
+/// </summary>
+public enum StockNature
+{
+    Stocked,
+    NonStocked,
+    Service
+}