sku and item fix

Backend/ERPCore/Domain/Entities/ItemType.cs

@@ -7,12 +7,15 @@ namespace ERPCore.Domain.Entities;
 /// 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
+/// nothing: there is no value table and no join to <see cref="Item"/>. 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>
+/// <para>
+/// It does, however, carry one piece of meaning the client acts on:
+/// <see cref="IsMeasurable"/>. So this is no longer purely a dropdown source.
+/// </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.
@@ -21,6 +24,24 @@ public class ItemType
 {
     public int ItemTypeId { get; set; }
     public string Name { get; set; } = string.Empty;
+
+    /// <summary>
+    /// When true, this dimension's values are content <b>measurements</b> (500 ml, 1 L) rather
+    /// than plain labels (Red, S). The item builder then captures a number + unit per value and
+    /// stamps that pair onto each generated item's <see cref="Item.ContentQty"/> /
+    /// <see cref="Item.ContentUnit"/>, instead of copying one form-level pair into every variant
+    /// — which is what makes "Coca-Cola in 500 ml / 1 L / 250 ml" three correctly sized items.
+    /// <para>
+    /// This is what lets an apparel <c>Size</c> (S/M/L) stay plain text while a
+    /// <c>Pack Size</c>/<c>Volume</c> dimension carries ml/g/L/kg.
+    /// </para>
+    /// <para>
+    /// A client hint only: the server never reads it when writing an item. Each item's pair is
+    /// still validated and normalised on its own by <c>ItemContent</c>.
+    /// </para>
+    /// </summary>
+    public bool IsMeasurable { get; set; }
+
     public EntityStatus Status { get; set; } = EntityStatus.Active;
 
     public DateTime CreatedAt { get; set; }