Stuck queued runner jobs are now automatically recovered

Runner jobs that become stranded in the queued phase are now automatically recovered. A new background worker periodically cross-checks stale queued jobs against GitHub: jobs that GitHub already reports as completed or pruned are reconciled to the correct terminal state, and a 24-hour backstop force-completes any row that is still stuck. Genuinely pending jobs are left untouched during the first hour, so normal queueing behavior is unaffected. The result is that the Runners dashboard will no longer show jobs stuck in the queued state indefinitely.