feat(purchase): 采购批次号支持，同一批提交的记录可分组查看/统计

背景: 循环提交把一批物品生成多条独立申请，无法识别'哪些是同一批采购'

后端:
- purchase_request 模型新增 batch_no 字段（同一批提交共享）
- create 接口接收 batch_no，无则自动生成 BATCH-yyyyMMdd-HHmm-随机
- 新增 GET /purchase/batch/<batch_no> 按批次查询所有记录
- 批量审批接口支持按 batch_no 一键审批整批

前端:
- 提交时生成 batch_no 共享给所有行
- 列表新增批次号列（可点击）
- 新增'整批查看'弹窗：显示同批次所有记录 + 一键批量通过本批
- 操作列新增'整批'按钮

数据库需执行: ALTER TABLE purchase_request ADD COLUMN batch_no VARCHAR(100);

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

@@ -157,6 +157,38 @@ def get_purchase_detail(purchase_id):
         return jsonify({'code': 500, 'msg': str(e)}), 500
 
 
+# --------------------------------------------------------
+# 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>
+# --------------------------------------------------------
+@purchase_bp.route('/batch/<path:batch_no>', 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"""
+    try:
+        from app.models.purchase import PurchaseRequest
+        records = PurchaseRequest.query.filter(
+            PurchaseRequest.batch_no == batch_no
+        ).order_by(PurchaseRequest.id.asc()).all()
+
+        user_id = get_current_user_id()
+        has_perm = _user_has_purchase_perm()
+
+        items = []
+        for r in records:
+            d = r.to_dict()
+            # 非本人且无权限时，价格字段剥离
+            if d['requester_id'] != user_id and not has_perm:
+                for k in ('unit_price', 'total_price', 'tax_rate'):
+                    d.pop(k, None)
+            items.append(d)
+
+        return jsonify({'code': 200, 'msg': '获取成功', 'data': {'batch_no': batch_no, 'items': items}}), 200
+    except Exception as e:
+        traceback.print_exc()
+        return jsonify({'code': 500, 'msg': str(e)}), 500
+
+
 # --------------------------------------------------------
 # 4. 审批采购申请
 # PATCH /api/v1/purchase/<id>/approve
@@ -214,7 +246,9 @@ def batch_approve_purchase():
 
     请求体:
     {
-        "ids": [1, 2, 3],
+        "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）
         "action": "approve" | "reject",
         "reject_reason": "驳回原因（reject 时必填）"
     }
@@ -223,11 +257,23 @@ 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')
         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:
+            from app.models.purchase import PurchaseRequest
+            records = PurchaseRequest.query.filter(
+                PurchaseRequest.batch_no == batch_no,
+                PurchaseRequest.status == 0
+            ).all()
+            ids = [r.id for r in records]
+            if not ids:
+                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 不能为空'}), 400
+            return jsonify({'code': 400, 'msg': 'ids 或 batch_no 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: