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

frontend/src/components/admin/usage/UsageCleanupDialog.vue

@@ -219,7 +219,7 @@ const loadTasks = async () => {
   if (!props.show) return
   tasksLoading.value = true
   try {
-    const res = await adminUsageAPI.listCleanupTasks({ page: 1, page_size: 10 })
+    const res = await adminUsageAPI.listCleanupTasks({ page: 1, page_size: 5 })
     tasks.value = res.items || []
   } catch (error) {
     console.error('Failed to load cleanup tasks:', error)