refactor(FE-212): add updateStaffApproval method and enhance PurchaseStaffApprovalItem schema with optional purchase_item_id

src/services/api/purchase.ts

@@ -3,6 +3,7 @@ import {
   Purchase,
   UpdatePurchaseRequestPayload,
   CreateStaffApprovalRequestPayload,
+  UpdateStaffApprovalRequestPayload,
   CreateManagerApprovalRequestPayload,
   CreateAcceptApprovalRequestPayload,
   DeletePurchaseRequestItemPayload,
@@ -19,7 +20,7 @@ export const PurchaseRequestApi = new BaseApiService<
 export class StaffApprovalService extends BaseApiService<
   Purchase,
   CreateStaffApprovalRequestPayload,
-  unknown
+  UpdateStaffApprovalRequestPayload
 > {
   constructor(basePath: string = '') {
     super(basePath);
@@ -37,6 +38,19 @@ export class StaffApprovalService extends BaseApiService<
       }
     );
   }
+
+  async updateStaffApproval(
+    purchaseRequestId: number,
+    payload: UpdateStaffApprovalRequestPayload
+  ): Promise<BaseApiResponse<{ message: string }> | undefined> {
+    return await this.customRequest<BaseApiResponse<{ message: string }>>(
+      `${purchaseRequestId}/approvals/staff`,
+      {
+        method: 'POST',
+        payload,
+      }
+    );
+  }
 }
 
 export class ManagerApprovalService extends BaseApiService<