fix: reset stock quantity color and enforce location validation for all inbound operations

inventory-backend/app/api/v1/inbound/buy.py

@@ -213,6 +213,11 @@ def submit():
                 if perm_code and perm_code not in user_permissions:
                     data.pop(field, None)
 
+        # 库位必填校验（安全兜底）
+        location = data.get('warehouse_location', '').strip()
+        if not location:
+            return jsonify({"code": 400, "msg": "入库失败：库位为必填项，不能为空！"}), 400
+
         new_stock = BuyInboundService.handle_inbound(data)
 
         return jsonify({