Add CancelStaleQueuedPublishTasks to abort publish tasks that sit in the
queue past a configurable timeout (default 3 days) without being claimed by
a desktop client, so they no longer linger indefinitely as 'queued'. The
lease recovery worker runs the cleanup each cycle and reports a
cancelled_queued count; the timeout is configurable via job run config.
Aborted tasks carry a publish_queue_timeout error payload with a readable
Chinese duration, and the admin-web publish summary surfaces it as an
auto-cancelled queue-timeout message.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
