Add item tracking migrations

Distribution/Models/Enums.cs

@@ -44,4 +44,6 @@ namespace Distribution.Models
     /// ModeB: Invoice created as a separate explicit step.
     /// </summary>
     public enum InvoiceCreationMode { ModeA, ModeB }
+
+    public enum SerialStatus { InStock, Sold, Returned, Damaged }
 }

Distribution/Models/Item.cs

@@ -32,6 +32,13 @@ namespace Distribution.Models
         /// <summary>Cost/purchase price, used to value free-goods scheme redemptions for getSchemeROI.</summary>
         public decimal? CostPrice { get; set; }
 
+        public bool TracksSerialNumbers { get; set; } = false;
+        public bool TracksBatches { get; set; } = false;
+        public bool TracksExpiryDate { get; set; } = false;
+        public bool HasWarranty { get; set; } = false;
+        public int? WarrantyPeriodDays { get; set; }
+        public bool AllowCustomWarrantyPeriod { get; set; } = false;
+
         public SyncSource SyncSource { get; set; } = SyncSource.Manual;
         public int? ExternalErpItemId { get; set; }
         public DateTime? LastSyncedAt { get; set; }

Distribution/Models/ItemBatch.cs

@@ -0,0 +1,20 @@
+using System.ComponentModel.DataAnnotations.Schema;
+
+namespace Distribution.Models
+{
+    /// <summary>
+    /// Backs both batch/lot tracking and expiry-only tracking for an item. BatchNumber is null
+    /// when the item tracks an expiry date but not a batch number (TracksExpiryDate without
+    /// TracksBatches).
+    /// </summary>
+    public class ItemBatch : Template
+    {
+        public Guid FK_ItemId { get; set; }
+        [ForeignKey("FK_ItemId")]
+        public Item Item { get; set; }
+
+        public string? BatchNumber { get; set; }
+        public DateTime? ManufactureDate { get; set; }
+        public DateTime? ExpiryDate { get; set; }
+    }
+}

Distribution/Models/ItemSerialNumber.cs

@@ -0,0 +1,26 @@
+using System.ComponentModel.DataAnnotations.Schema;
+
+namespace Distribution.Models
+{
+    /// <summary>One row per physical serial-tracked unit. Quantity is always 1.</summary>
+    public class ItemSerialNumber : Template
+    {
+        public Guid FK_ItemId { get; set; }
+        [ForeignKey("FK_ItemId")]
+        public Item Item { get; set; }
+
+        public string SerialNumber { get; set; }
+        public SerialStatus Status { get; set; } = SerialStatus.InStock;
+
+        public Guid? CurrentLocationId { get; set; }
+        public LocationType? CurrentLocationType { get; set; }
+
+        public DateTime ReceivedAt { get; set; }
+
+        /// <summary>Snapshotted at receipt when Item.AllowCustomWarrantyPeriod is true; otherwise null and the system default applies when the warranty starts.</summary>
+        public int? WarrantyPeriodDaysOverride { get; set; }
+
+        /// <summary>Set when the serial is sold/delivered: sale date + (override ?? system default). Null while in stock or if Item.HasWarranty is false.</summary>
+        public DateTime? WarrantyExpiresAt { get; set; }
+    }
+}

Distribution/Models/StockBalance.cs

@@ -13,6 +13,16 @@ namespace Distribution.Models
         public Guid LocationId { get; set; }
         public LocationType LocationType { get; set; }
 
+        /// <summary>Null for items that don't track batches/expiry — no behavior change for existing items.</summary>
+        public Guid? FK_ItemBatchId { get; set; }
+        [ForeignKey("FK_ItemBatchId")]
+        public ItemBatch? ItemBatch { get; set; }
+
+        /// <summary>Null for items that don't track serial numbers.</summary>
+        public Guid? FK_ItemSerialNumberId { get; set; }
+        [ForeignKey("FK_ItemSerialNumberId")]
+        public ItemSerialNumber? ItemSerialNumber { get; set; }
+
         public decimal Quantity { get; set; }
         public DateTime UpdatedAt { get; set; } = DateTime.Now;
     }

Distribution/Models/StockMovement.cs

@@ -16,6 +16,16 @@ namespace Distribution.Models
         public Guid? ToLocationId { get; set; }
         public LocationType? ToLocationType { get; set; }
 
+        /// <summary>Null for items that don't track batches/expiry — no behavior change for existing items.</summary>
+        public Guid? FK_ItemBatchId { get; set; }
+        [ForeignKey("FK_ItemBatchId")]
+        public ItemBatch? ItemBatch { get; set; }
+
+        /// <summary>Null for items that don't track serial numbers. Quantity is always 1 when set.</summary>
+        public Guid? FK_ItemSerialNumberId { get; set; }
+        [ForeignKey("FK_ItemSerialNumberId")]
+        public ItemSerialNumber? ItemSerialNumber { get; set; }
+
         public decimal Quantity { get; set; }
         public MovementType Type { get; set; }