refactor(ao): background loops only orchestrate; cleanup/reconcile endpoints enqueue

- separate qB sync timer from the planning timer
- threshold cleanup, reserved-plan and pending-import sweeps, 6h reconcile enqueue
  engine tasks with time-slot idempotency keys instead of running inline
- pending-import sweep selects by completed_at (sync refreshes updated_at every round)
- POST /download-cache/cleanup and /library/reconcile return {taskId, runId} (202);
  web jumps to the engine run page
- test: a 50MB verifyAndImport in progress does not delay qB sync

Co-Authored-By: Claude Opus 5.5 <[email protected]>

apps/web/app/api/downloads.ts

@@ -102,14 +102,14 @@ export function useCacheVolumes() {
   });
 }
 
-/** 手动清理:只清已验证入库且满足保留/H&R 的纳管任务 */
+/** 手动清理:服务端入队 cleanupDownloadCache(只清已验证入库且满足保留/H&R 的纳管任务),返回任务 id */
 export function useCacheCleanup() {
   const qc = useQueryClient();
   return useMutation({
     mutationFn: (downloaderInstanceId?: string) =>
       apiMutate("/api/v1/download-cache/cleanup", {
         body: downloaderInstanceId ? { downloaderInstanceId } : {},
-      }).then((d) => z.object({ report: z.record(z.string(), z.unknown()) }).parse(d)),
+      }).then((d) => z.object({ taskId: z.string(), runId: z.string() }).parse(d)),
     onSuccess: () => qc.invalidateQueries({ queryKey: downloadKeys.all }),
   });
 }