Long-running maintenance tasks must survive navigating away or reloading
the page. VideoDedupCard + GatedPurgeCard held the in-flight Celery task id
only in component refs and polled task-result inline, so leaving the page
mid-run lost the id and the result was never shown — even though the task
finished on the worker.
New shared composable useMaintenanceTask: persists {taskId, mode, startedAt}
to localStorage on dispatch, re-attaches on mount, and re-shows the result
when the task finishes (the celery result backend retains the summary well
under result_expires). Stale-guard skips resume past 3h. Both cards refactored
onto it; card-specific computeds + confirm dialog kept.
Also fixed the QueueStatusBar lane: both cards watched queue="maintenance"
but tasks.admin.* routes to maintenance_long, so the bar never reflected
their own task — now queue="maintenance_long".
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
bvandeusen