refactor(purchase): 批次概念改为基于 request_no 前缀推导，撤销数据库字段

按用户反馈：不需要新增数据库字段，现有 request_no (PUR-20260831-1021-0001)
本身就能推导批次——去掉末尾4位流水号即为批次前缀。

- 撤销 purchase_request.batch_no 字段（模型/数据库）
- 撤销 create 接口的 batch_no 参数与 generate_batch_no
- 批次标识 = request_no 去掉末尾 -XXXX 段
  getBatchKey('PUR-20260831-1021-0001') = 'PUR-20260831-1021'
- 按批次查询/批量审批接口改用 batch_key (request_no LIKE 前缀)
- 前端列表批次号列、整批弹窗、一键审批本批均基于前缀推导
- 零数据库迁移，历史数据立即可用

inventory-backend/app/api/v1/purchase.py

@@ -158,18 +158,18 @@ def get_purchase_detail(purchase_id):
 
 
 # --------------------------------------------------------
-# 3.5 按批次查询采购申请（同一批提交的多条记录）
-# GET /api/v1/purchase/batch/<batch_no>
+# 3.5 按批次查询采购申请（同一批提交的多条记录，批次=request_no去掉末尾流水号）
+# GET /api/v1/purchase/batch/<batch_key>
 # --------------------------------------------------------
-@purchase_bp.route('/batch/<path:batch_no>', methods=['GET'])
+@purchase_bp.route('/batch/<path:batch_key>', methods=['GET'])
 @jwt_required()
-def get_purchase_by_batch(batch_no):
-    """按批次号查询同一批提交的所有采购申请记录"""
+def get_purchase_by_batch(batch_key):
+    """按批次前缀（request_no 去掉末尾4位流水号）查询同一批的所有记录"""
     try:
         from app.models.purchase import PurchaseRequest
         records = PurchaseRequest.query.filter(
-            PurchaseRequest.batch_no == batch_no
-        ).order_by(PurchaseRequest.id.asc()).all()
+            PurchaseRequest.request_no.like(f"{batch_key}-%")
+        ).order_by(PurchaseRequest.request_no.asc()).all()
 
         user_id = get_current_user_id()
         has_perm = _user_has_purchase_perm()
@@ -183,7 +183,7 @@ def get_purchase_by_batch(batch_no):
                     d.pop(k, None)
             items.append(d)
 
-        return jsonify({'code': 200, 'msg': '获取成功', 'data': {'batch_no': batch_no, 'items': items}}), 200
+        return jsonify({'code': 200, 'msg': '获取成功', 'data': {'batch_key': batch_key, 'items': items}}), 200
     except Exception as e:
         traceback.print_exc()
         return jsonify({'code': 500, 'msg': str(e)}), 500
@@ -248,7 +248,7 @@ def batch_approve_purchase():
     {
         "ids": [1, 2, 3],            // 按 ID 列表审批
         或
-        "batch_no": "BATCH-xxx",     // 按批次号审批整批（同一批提交的记录）
+        "batch_key": "PUR-20260831-1021",  // 按批次前缀审批整批（同批流水号连续）
         "action": "approve" | "reject",
         "reject_reason": "驳回原因（reject 时必填）"
     }
@@ -257,15 +257,15 @@ def batch_approve_purchase():
         user_id = get_current_user_id()
         data = request.get_json() or {}
         ids = data.get('ids', [])
-        batch_no = data.get('batch_no')
+        batch_key = data.get('batch_key')
         action = data.get('action', 'approve')
         reject_reason = data.get('reject_reason')
 
-        # 若传 batch_no，则查出该批次的所有待审批记录 ID
-        if batch_no:
+        # 若传 batch_key（request_no 去掉末尾流水号的前缀），查出该批次所有待审批记录
+        if batch_key:
             from app.models.purchase import PurchaseRequest
             records = PurchaseRequest.query.filter(
-                PurchaseRequest.batch_no == batch_no,
+                PurchaseRequest.request_no.like(f"{batch_key}-%"),
                 PurchaseRequest.status == 0
             ).all()
             ids = [r.id for r in records]
@@ -273,7 +273,7 @@ def batch_approve_purchase():
                 return jsonify({'code': 400, 'msg': '该批次没有待审批的记录'}), 400
 
         if not ids or not isinstance(ids, list):
-            return jsonify({'code': 400, 'msg': 'ids 或 batch_no 不能为空'}), 400
+            return jsonify({'code': 400, 'msg': 'ids 或 batch_key 不能为空'}), 400
         if action not in ('approve', 'reject'):
             return jsonify({'code': 400, 'msg': '无效的审批操作'}), 400
         if action == 'reject' and not reject_reason: