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.

Frontend/erp-system/lib/validations/grn.ts

@@ -3,7 +3,7 @@
 // (over-receipt tolerance, referential existence, concurrency) are never
 // re-implemented here; the server's ProblemDetails is the final word (§3.3).
 import { z } from "zod"
-import { TrackingMode } from "@/types/master-data"
+import { Warranty } from "@/types/master-data"
 
 export const grnHeaderSchema = z.object({
   warehouseId: z.number({ error: "Select a warehouse" }).positive("Select a warehouse"),
@@ -17,9 +17,8 @@ export function validateLine(input: {
   unitCost: string
   discountPct: string
   vatPct: string
-  trackingMode: TrackingMode | null
-  batchNo: string
-  serialNumbersText: string
+  warranty: Warranty | null
+  warrantyNumbers: string[]
 }): Record<string, string> {
   const errors: Record<string, string> = {}
 
@@ -39,27 +38,16 @@ export function validateLine(input: {
   if (input.vatPct !== "" && (Number.isNaN(vatPct) || vatPct < 0 || vatPct > 100))
     errors.vatPct = "VAT must be 0–100%"
 
-  if (input.trackingMode === "Batch" && !input.batchNo.trim()) {
-    errors.batchNo = "Batch number is required for this item"
-  }
-
-  if (input.trackingMode === "Serial") {
-    const serials = splitSerials(input.serialNumbersText)
-    if (serials.length === 0) {
-      errors.serialNumbers = "Enter one serial number per unit"
-    } else if (!Number.isNaN(qty) && serials.length !== qty) {
-      errors.serialNumbers = `Enter exactly ${qty || 0} serial number(s) — got ${serials.length}`
-    } else if (new Set(serials).size !== serials.length) {
-      errors.serialNumbers = "Serial numbers must be unique"
+  if (input.warranty === "Warranty") {
+    const numbers = input.warrantyNumbers.map((s) => s.trim()).filter((s) => s.length > 0)
+    if (numbers.length === 0) {
+      errors.warrantyNumbers = "Enter one warranty number per unit"
+    } else if (!Number.isNaN(qty) && numbers.length !== qty) {
+      errors.warrantyNumbers = `Enter exactly ${qty || 0} warranty number(s) — got ${numbers.length}`
+    } else if (new Set(numbers.map((s) => s.toLowerCase())).size !== numbers.length) {
+      errors.warrantyNumbers = "Warranty numbers must be unique"
     }
   }
 
   return errors
 }
-
-export function splitSerials(text: string): string[] {
-  return text
-    .split(/[\n,]/)
-    .map((s) => s.trim())
-    .filter((s) => s.length > 0)
-}