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/Infra/Persistence/Configurations/GrnConfiguration.cs

@@ -53,3 +53,21 @@ public sealed class GrnLineConfiguration : IEntityTypeConfiguration<GrnLine>
         builder.HasOne(l => l.Batch).WithMany().HasForeignKey(l => l.BatchId).OnDelete(DeleteBehavior.Restrict);
     }
 }
+
+public sealed class GrnLineWarrantyNumberConfiguration : IEntityTypeConfiguration<GrnLineWarrantyNumber>
+{
+    public void Configure(EntityTypeBuilder<GrnLineWarrantyNumber> builder)
+    {
+        builder.ToTable("grn_line_warranty_numbers");
+        builder.HasKey(w => w.GrnLineWarrantyNumberId);
+
+        builder.Property(w => w.WarrantyNo).IsRequired().HasMaxLength(100);
+
+        builder.HasOne(w => w.GrnLine).WithMany(l => l.WarrantyNumbers)
+            .HasForeignKey(w => w.GrnLineId).OnDelete(DeleteBehavior.Cascade);
+
+        // A warranty number entered twice on the same line is almost certainly a typo —
+        // catch it at the DB, not just client-side.
+        builder.HasIndex(w => new { w.GrnLineId, w.WarrantyNo }).IsUnique();
+    }
+}

Backend/ERPCore/Infra/Persistence/Configurations/ItemConfiguration.cs

@@ -36,6 +36,9 @@ public sealed class ItemConfiguration : IEntityTypeConfiguration<Item>
             .HasConversion<string>().HasMaxLength(20).IsRequired();
         builder.Property(i => i.TrackingMode)
             .HasConversion<string>().HasMaxLength(20).IsRequired();
+        builder.Property(i => i.Warranty)
+            .HasConversion<string>().HasMaxLength(20).IsRequired()
+            .HasDefaultValue(Warranty.NonWarranty);
         builder.Property(i => i.Status)
             .HasConversion<string>().HasMaxLength(20).IsRequired()
             .HasDefaultValue(EntityStatus.Active);