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/api/access-config.ts

@@ -0,0 +1,21 @@
+// Access configuration. Singleton - no id. The default role is what a first sign-in (or a person with no role) receives.
+import { apiRequestWithETag } from "@/lib/api-client"
+import { ApiResult } from "@/types/common"
+
+export interface AccessConfig {
+  defaultRoleId: number | null
+  defaultRoleName: string | null
+  updatedAt: string | null
+  updatedBy: number | null
+}
+
+export const accessConfigApi = {
+  get(): Promise<ApiResult<AccessConfig>> {
+    return apiRequestWithETag<AccessConfig>("/access-config")
+  },
+
+  /** `null` clears the default (people without a role then have no permissions at all). The administrator role is refused. */
+  update(defaultRoleId: number | null, ifMatch: string): Promise<ApiResult<AccessConfig>> {
+    return apiRequestWithETag<AccessConfig>("/access-config", { method: "PUT", body: { defaultRoleId }, ifMatch })
+  },
+}

Frontend/erp-system/lib/api/grns.ts

@@ -27,6 +27,11 @@ export interface ListGrnsParams {
   vendorId?: number
   warehouseId?: number
   branchId?: number
+  /** Created on or after this day (YYYY-MM-DD). */
+  from?: string
+  /** Created on or before this day (YYYY-MM-DD). */
+  to?: string
+  /** `created` (default, newest first) | `vendor` | `total` | `status`; a leading `-` flips the direction. */
   sort?: string
 }
 

Frontend/erp-system/lib/api/opening-balances.ts

@@ -0,0 +1,40 @@
+// Opening balances. post() creates ONE journal in the General Ledger (a debit per cash/bank account, the
+// offsetting credit to "Opening Balance Equity") and can be done only once: a second call is 409
+// OPENING_BALANCE_ALREADY_POSTED.
+import { apiRequest } from "@/lib/api-client"
+import {
+  CashBankOpeningState,
+  OpeningBalanceRun,
+  OpeningStockRun,
+  OpeningStockRunSummary,
+  PostCashBankOpeningRequest,
+  PostOpeningStockRequest,
+} from "@/types/opening-balances"
+
+export const openingBalancesApi = {
+  /** The cash/bank accounts to enter amounts for — or the posted record, once it has been done. */
+  cashBank(): Promise<CashBankOpeningState> {
+    return apiRequest<CashBankOpeningState>("/opening-balances/cash-bank")
+  },
+
+  postCashBank(request: PostCashBankOpeningRequest): Promise<OpeningBalanceRun> {
+    return apiRequest<OpeningBalanceRun>("/opening-balances/cash-bank", { method: "POST", body: request })
+  },
+
+  /** Opening-stock runs posted so far, newest first. */
+  stockRuns(): Promise<OpeningStockRunSummary[]> {
+    return apiRequest<OpeningStockRunSummary[]>("/opening-balances/stock")
+  },
+
+  stockRun(runId: number): Promise<OpeningStockRun> {
+    return apiRequest<OpeningStockRun>(`/opening-balances/stock/${runId}`)
+  },
+
+  /**
+   * Creates a FIFO layer per line and ONE journal (Dr Inventory / Cr Opening Balance Equity). 409 when an item
+   * already has stock movements in that warehouse; untracked, stocked items only.
+   */
+  postStock(request: PostOpeningStockRequest): Promise<OpeningStockRun> {
+    return apiRequest<OpeningStockRun>("/opening-balances/stock", { method: "POST", body: request })
+  },
+}

Frontend/erp-system/lib/api/procurement-config.ts

@@ -0,0 +1,22 @@
+// Procurement configuration. Singleton - no id. Controls the optional vendor contact / address
+// fields and whether purchase orders carry tax. The server enforces every flag too: a value sent
+// for a switched-off field returns 422 CONFIG_DISABLED, so the UI hides what is off.
+import { apiRequest, apiRequestWithETag } from "@/lib/api-client"
+import { ApiResult } from "@/types/common"
+import { ProcurementConfig, UpdateProcurementConfigRequest } from "@/types/procurement"
+
+export const procurementConfigApi = {
+  get(): Promise<ApiResult<ProcurementConfig>> {
+    return apiRequestWithETag<ProcurementConfig>("/procurement-config")
+  },
+
+  /** Full replacement — every flag is required. */
+  update(request: UpdateProcurementConfigRequest, ifMatch: string): Promise<ApiResult<ProcurementConfig>> {
+    return apiRequestWithETag<ProcurementConfig>("/procurement-config", { method: "PUT", body: request, ifMatch })
+  },
+}
+
+/** Read-only helper for screens that only need the flags. */
+export function procurementConfig(): Promise<ProcurementConfig> {
+  return apiRequest<ProcurementConfig>("/procurement-config")
+}

Frontend/erp-system/lib/api/purchase-orders.ts

@@ -18,13 +18,18 @@ export interface ListPurchaseOrdersParams {
   q?: string
   status?: PurchaseOrderStatus
   vendorId?: number
+  /** Created on or after this day (YYYY-MM-DD). */
+  from?: string
+  /** Created on or before this day (YYYY-MM-DD). */
+  to?: string
+  /** `created` (default, newest first) | `vendor` | `total` | `status`; a leading `-` flips the direction. */
   sort?: string
 }
 
-/** Editable/deletable only while Draft (FR-PROC-05, revised — submitting locks the PO).
+/** Editable/deletable only while Draft or Rejected (FR-PROC-05, revised — submitting locks the PO; a rejected one is reopened for revision).
  *  The server is authoritative (409 PO_NOT_EDITABLE otherwise); this only drives UI affordances. */
 export function isPoEditable(status: PurchaseOrderStatus): boolean {
-  return status === "Draft"
+  return status === "Draft" || status === "Rejected"
 }
 
 export const purchaseOrdersApi = {

Frontend/erp-system/lib/api/users.ts

@@ -21,6 +21,8 @@ export interface ListUsersParams {
   q?: string
   status?: EntityStatus
   roleCode?: string
+  /** true = only administrators (users whose role is the administrator role, whatever it is called). */
+  isAdmin?: boolean
 }
 
 export const usersApi = {