- execution_service 新增 recover_interrupted_executions：启动把超龄 running/pending
  UI 执行标 failed，同步其 pending/running 用例结果
- scheduler_service run_task_once 新增 DB 级兜底：内存锁为空但 DB 仍有 running/pending
  UI 执行时跳过触发并推进 next_run_at
- main lifespan 启动调用恢复，打印清理日志
- 新增 test_scheduler_recovery 5 项测试
Co-Authored-By: Claude <noreply@anthropic.com>