fix：sort时有类型转换异常

src/main/java/com/ai/da/service/impl/CollectionSortServiceImpl.java

@@ -100,7 +100,7 @@ public class CollectionSortServiceImpl extends ServiceImpl<CollectionSortMapper,
         throw new BusinessException("获取排序号失败");
     }
 
-    private Long getMaxSortFromDB(Long projectId, Long parentId) {
+    private Integer getMaxSortFromDB(Long projectId, Long parentId) {
         QueryWrapper<CollectionSort> qw = new QueryWrapper<>();
         qw.select("COALESCE(MAX(sort), 0) as maxSort")
                 .eq("project_id", projectId);