feat: add vendor optional fields and configuration hooks

- Implemented VendorOptionalFields component to handle optional vendor details (mobile, email, address) with validation.
- Created useCustomerConfig hook to load optional customer field settings from Sales configuration.
- Developed useProcurementConfig hook to manage Procurement configuration flags.
- Introduced accessConfigApi for managing access configuration settings.
- Added openingBalancesApi for handling opening balances operations.
- Created procurementConfigApi for managing procurement configuration settings.
- Implemented nav-routes for permission-based routing.
- Developed PDF generation for purchase orders with dynamic vendor and item details.
- Added purchase-order tax helpers for tax calculations and formatting.
- Defined types for opening balances and related operations.

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

@@ -46,6 +46,7 @@ export function validatePoLine(input: {
   if (input.unitPrice === "" || Number.isNaN(unitPrice) || unitPrice < 0) errors.unitPrice = "Unit price cannot be negative"
   const tax = Number(input.tax)
   if (input.tax === "" || Number.isNaN(tax) || tax < 0) errors.tax = "Tax rate cannot be negative"
+  else if (tax > 1) errors.tax = "Tax cannot exceed 100%"
   return errors
 }