fix(admin): 修复预订单购物车信息逻辑

- 在预订单购物车信息中添加 purchase 字段，用于记录商品价格
- 修复了未定义 prices 导致的潜在问题，使用空值合并运算符 ?? 0 提供默认值
- 确保 cart_num、accept_num 和 price 字段正确赋值

app/admin/logic/beforehand_order_cart_info/BeforehandOrderCartInfoLogic.php

@@ -82,6 +82,7 @@ class BeforehandOrderCartInfoLogic extends BaseLogic
                 $datas[$k]['bhoid'] = $bhoid;
                 $datas[$k]['cart_num'] = $v['nums'];
                 $datas[$k]['accept_num'] = $v['nums'];
+                $datas[$k]['purchase'] = $v['prices']??0;
                 $datas[$k]['price'] = $v['purchase'];
                 $datas[$k]['total_price'] = $v['total_price'];
                 $datas[$k]['pay_price'] = $v['total_price'];