perf(shop): 优化经销商设置列表排序逻辑

- 将默认排序字段从 create_time 改为 update_time
- 移除 PageParam 的排序方法，改用 Java Stream 的 sort 进行排序
- 添加空值检查，避免对空列表进行排序操作
- 使用 Comparator.nullsLast 处理空值情况
- 提升列表排序性能，减少不必要的对象创建

src/main/java/com/gxwebsoft/shop/service/impl/ShopDealerSettingServiceImpl.java

@@ -10,6 +10,7 @@ import com.gxwebsoft.common.core.web.PageResult;
 import com.baomidou.mybatisplus.core.conditions.query.LambdaQueryWrapper;
 import org.springframework.stereotype.Service;
 
+import java.util.Comparator;
 import java.util.List;
 
 /**
@@ -24,7 +25,7 @@ public class ShopDealerSettingServiceImpl extends ServiceImpl<ShopDealerSettingM
     @Override
     public PageResult<ShopDealerSetting> pageRel(ShopDealerSettingParam param) {
         PageParam<ShopDealerSetting, ShopDealerSettingParam> page = new PageParam<>(param);
-        page.setDefaultOrder("create_time desc");
+        page.setDefaultOrder("update_time desc");
         List<ShopDealerSetting> list = baseMapper.selectPageRel(page, param);
         return new PageResult<>(list, page.getTotal());
     }
@@ -32,10 +33,14 @@ public class ShopDealerSettingServiceImpl extends ServiceImpl<ShopDealerSettingM
     @Override
     public List<ShopDealerSetting> listRel(ShopDealerSettingParam param) {
         List<ShopDealerSetting> list = baseMapper.selectListRel(param);
-        // 排序
-        PageParam<ShopDealerSetting, ShopDealerSettingParam> page = new PageParam<>();
-        page.setDefaultOrder("create_time desc");
-        return page.sortRecords(list);
+        if (list == null || list.size() < 2) {
+            return list;
+        }
+        list.sort(Comparator.comparing(
+            ShopDealerSetting::getUpdateTime,
+            Comparator.nullsLast(Integer::compareTo)
+        ).reversed());
+        return list;
     }
 
     @Override