feat: add warranty tracking for items and GRN lines

- Enhanced ItemService to include warranty and warranty period months in item DTOs.
- Implemented validation for warranty periods in ItemService.
- Updated frontend item detail and new item pages to handle warranty selection and input.
- Added warranty number handling in GRN creation and detail pages.
- Introduced new GrnLineWarrantyNumber entity to capture warranty numbers for received items.
- Created Warranty enum and associated allowed months for warranty coverage.
- Updated validation logic for GRN lines to ensure warranty numbers are captured correctly.

Backend/ERPCore/Services/GrnService.cs

@@ -91,7 +91,7 @@ public sealed class GrnService : IGrnService
     public async Task<GrnDto?> GetAsync(int grnId, CancellationToken ct = default)
     {
         var grn = await _grns.Query().AsNoTracking()
-            .Include(g => g.Lines)
+            .Include(g => g.Lines).ThenInclude(l => l.WarrantyNumbers)
             .FirstOrDefaultAsync(g => g.GrnId == grnId, ct);
         return grn is null ? null : Map(grn);
     }
@@ -165,6 +165,7 @@ public sealed class GrnService : IGrnService
             var vatAmount = Math.Round(receivedValue * input.VatPct / 100m, 4, MidpointRounding.AwayFromZero);
 
             var batch = await ResolveBatchAsync(item, input.Batch, batchCache, ct);
+            var warrantyNumbers = ResolveWarrantyNumbers(item, input.WarrantyNumbers, input.Qty);
 
             lines.Add(new GrnLine
             {
@@ -181,7 +182,8 @@ public sealed class GrnService : IGrnService
                 VatAmount = vatAmount,
                 ReceivedValue = receivedValue,
                 LineTotal = receivedValue + vatAmount,
-                HoldStatus = input.HoldStatus
+                HoldStatus = input.HoldStatus,
+                WarrantyNumbers = warrantyNumbers
             });
         }
 
@@ -341,6 +343,30 @@ public sealed class GrnService : IGrnService
         return created; // linked via GrnLine.Batch navigation; FK fixed up on SaveChanges
     }
 
+    /// <summary>
+    /// A warranty-tracked item requires exactly one warranty number per received unit —
+    /// same shape of rule as <see cref="ResolveBatchAsync"/> for batch tracking. The coverage
+    /// period is not entered at receipt; it is snapshotted from <see cref="Item.WarrantyPeriodMonths"/>,
+    /// which the item must have been given at creation (<see cref="ItemService"/> enforces that).
+    /// </summary>
+    private static List<GrnLineWarrantyNumber> ResolveWarrantyNumbers(Item item, List<string>? numbers, decimal qty)
+    {
+        if (item.Warranty != Warranty.Warranty) return new List<GrnLineWarrantyNumber>();
+        if (item.WarrantyPeriodMonths is null)
+            throw new DomainException(
+                ErrorCodes.Validation, $"Item {item.Sku} is under warranty but has no warranty period configured.", 422);
+
+        var trimmed = (numbers ?? new List<string>()).Select(n => n.Trim()).Where(n => n.Length > 0).ToList();
+        if (trimmed.Count != qty)
+            throw new DomainException(
+                ErrorCodes.Validation,
+                $"Item {item.Sku} is under warranty; provide exactly {qty} warranty number(s), got {trimmed.Count}.", 422);
+        if (trimmed.Distinct(StringComparer.OrdinalIgnoreCase).Count() != trimmed.Count)
+            throw new DomainException(ErrorCodes.Validation, $"Warranty numbers for item {item.Sku} must be unique.", 422);
+
+        return trimmed.Select(n => new GrnLineWarrantyNumber { WarrantyNo = n, WarrantyPeriodMonths = item.WarrantyPeriodMonths.Value }).ToList();
+    }
+
     private async Task UpdatePoStatusAsync(int? poId, CancellationToken ct)
     {
         if (poId is null) return;
@@ -382,5 +408,6 @@ public sealed class GrnService : IGrnService
             l.GrnLineId, l.PoLineId, l.ItemId, l.BinId, l.Qty, l.UnitCost, l.PoUnitPrice,
             l.DiscountPct, l.NetUnitCost, l.VatPct, l.VatAmount, l.ReceivedValue, l.LineTotal,
             l.PoUnitPrice is null ? 0m : Math.Round((l.UnitCost - l.PoUnitPrice.Value) * l.Qty, 4, MidpointRounding.AwayFromZero),
-            l.HoldStatus, l.BatchId)).ToList());
+            l.HoldStatus, l.BatchId,
+            l.WarrantyNumbers.Select(w => new GrnLineWarrantyNumberDto(w.WarrantyNo, w.WarrantyPeriodMonths)).ToList())).ToList());
 }

Backend/ERPCore/Services/ItemService.cs

@@ -85,7 +85,7 @@ public sealed class ItemService : IItemService
             .Select(i => new ItemListItemDto(
                 i.ItemId, i.Sku, i.Name, i.CategoryId, i.SubCategoryId, i.BrandId,
                 i.BaseUomId, i.DefaultVendorId,
-                i.StockNature, i.TrackingMode, i.TaxClass, i.SalePrice,
+                i.StockNature, i.TrackingMode, i.Warranty, i.WarrantyPeriodMonths, i.TaxClass, i.SalePrice,
                 i.ContentQty, i.ContentUnit, i.ContentBaseQty, i.ContentBaseUnit,
                 i.Status))
             .ToListAsync(ct);
@@ -113,6 +113,7 @@ 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 item = new Item
         {
@@ -126,6 +127,8 @@ public sealed class ItemService : IItemService
             DefaultVendorId = request.DefaultVendorId,
             StockNature = request.StockNature,
             TrackingMode = request.TrackingMode,
+            Warranty = request.Warranty,
+            WarrantyPeriodMonths = warrantyPeriodMonths,
             TaxClass = request.TaxClass,
             SalePrice = request.SalePrice,
             ContentQty = request.ContentQty,
@@ -172,6 +175,7 @@ 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);
 
         item.Sku = request.Sku.Trim();
         item.Name = request.Name.Trim();
@@ -183,6 +187,8 @@ public sealed class ItemService : IItemService
         item.DefaultVendorId = request.DefaultVendorId;
         item.StockNature = request.StockNature;
         item.TrackingMode = request.TrackingMode;
+        item.Warranty = request.Warranty;
+        item.WarrantyPeriodMonths = warrantyPeriodMonths;
         item.TaxClass = request.TaxClass;
         item.SalePrice = request.SalePrice;
         item.ContentQty = request.ContentQty;
@@ -326,6 +332,23 @@ 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.
+    /// </summary>
+    private static int? ValidateWarrantyPeriod(Warranty warranty, int? warrantyPeriodMonths)
+    {
+        if (warranty != Warranty.Warranty) return null;
+
+        if (warrantyPeriodMonths is null || !WarrantyPeriods.AllowedMonths.Contains(warrantyPeriodMonths.Value))
+            throw new DomainException(
+                ErrorCodes.Validation,
+                $"Warranty period must be one of {string.Join(", ", WarrantyPeriods.AllowedMonths)} months.", 422);
+
+        return warrantyPeriodMonths;
+    }
+
     private async Task SaveGuardingConcurrencyAsync(CancellationToken ct)
     {
         try
@@ -341,7 +364,7 @@ public sealed class ItemService : IItemService
     private static ItemDetailDto ToDetail(Item i) => new(
         i.ItemId, i.Sku, i.Name, i.Description, i.CategoryId, i.SubCategoryId, i.BrandId,
         i.BaseUomId, i.DefaultVendorId,
-        i.StockNature, i.TrackingMode, i.TaxClass, i.SalePrice,
+        i.StockNature, i.TrackingMode, i.Warranty, i.WarrantyPeriodMonths, i.TaxClass, i.SalePrice,
         i.ContentQty, i.ContentUnit, i.ContentBaseQty, i.ContentBaseUnit,
         i.Status,
         i.ReorderSettings