feat(清理任务): 引入Ent存储并补充日志与测试

新增 usage_cleanup_task Ent schema 与仓储实现，支持清理任务排序分页
补充清理任务全链路日志、仪表盘重算触发及 UI 过滤调整
完善 repository/service 单测并引入 sqlite 测试依赖

backend/ent/predicate/predicate.go

@@ -33,6 +33,9 @@ type RedeemCode func(*sql.Selector)
 // Setting is the predicate function for setting builders.
 type Setting func(*sql.Selector)
 
+// UsageCleanupTask is the predicate function for usagecleanuptask builders.
+type UsageCleanupTask func(*sql.Selector)
+
 // UsageLog is the predicate function for usagelog builders.
 type UsageLog func(*sql.Selector)