调整购买产品优惠列表排序逻辑

在PurchaseProductOfferLists类中，修改了查询排序逻辑，先按product_id降序排列，然后在按id降序排列。这样可以更合理地组织返回的列表，根据产品ID进行分组，每组内部再按照记录ID降序排序。

app/api/lists/purchase_product_offer/PurchaseProductOfferLists.php

@@ -51,7 +51,7 @@ class PurchaseProductOfferLists extends BaseApiDataLists implements ListsSearchI
         return PurchaseProductOffer::where($this->searchWhere)
             ->field(['id', 'order_id', 'product_id', 'price', 'buyer_nums', 'unit', 'is_buyer', 'buyer_confirm','need_num', 'buyer_id', 'status', 'mark'])
             ->limit($this->limitOffset, $this->limitLength)
-            ->order(['id' => 'desc'])
+            ->order(['product_id'=>'desc','id' => 'desc'])
             ->select()->each(function($item){
                 $find=StoreProduct::where('id',$item->product_id)->find();
                 $item->store_name=$find->store_name;