feat(procurement): enhance purchase order and GRN functionalities

- Updated purchase order descriptions for clarity on draft and submission processes.
- Implemented submit and delete functionalities for draft purchase orders, allowing users to manage their orders more effectively.
- Added discount and VAT fields to GRN lines, enabling better cost tracking and reporting.
- Enhanced validation for GRN lines to ensure discount and VAT percentages are within acceptable ranges.
- Updated API to support new functionalities, including submitting and deleting purchase orders.
- Improved UI components for better user experience in managing purchase orders and GRNs.
- Documented changes in security and backend phase documentation to reflect new processes and requirements.

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

@@ -16,6 +16,8 @@ export function validateLine(input: {
   uomId: number | null
   qty: string
   unitCost: string
+  discountPct: string
+  vatPct: string
   trackingMode: TrackingMode | null
   batchNo: string
   serialNumbersText: string
@@ -31,6 +33,14 @@ export function validateLine(input: {
   const unitCost = Number(input.unitCost)
   if (input.unitCost === "" || Number.isNaN(unitCost) || unitCost < 0) errors.unitCost = "Unit cost cannot be negative"
 
+  const discountPct = Number(input.discountPct)
+  if (input.discountPct !== "" && (Number.isNaN(discountPct) || discountPct < 0 || discountPct > 100))
+    errors.discountPct = "Discount must be 0–100%"
+
+  const vatPct = Number(input.vatPct)
+  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"
   }