Add per-job "Run now" buttons and a "Start all now" button to the admin Scheduler
dashboard (admin-gated endpoints). Triggers run the job in a background thread
independent of its interval, refusing a concurrent run (409). While running, the
long jobs (maintenance, enrich, backfill, shorts) report live progress through a
decoupled contextvar sink, shown as a progress bar on the job row via the existing
4s poll. A manually-triggered run posts a completion notification to the triggering
admin's inbox (scheduled runs stay silent to avoid spam); the inbox renders the
"scheduler" type trilingually from type+data. While here, give the maintenance job
its missing dashboard label/description in all three languages.
Each job shows a tooltip (what it does + what happens if it stops), a status
dot legend + per-dot tooltips clarify the colours, and the interval is inline-
editable (pencil -> number -> save) wired to the new PATCH endpoint. HU/EN/DE.
New admin Scheduler page (left-nav entry) with a live, self-refreshing view of
job activity, queued work and quota. Polling is factored into a reusable
useLiveQuery hook (pauses when the tab is unfocused) that the notification bell
and future yt-dlp job queue will reuse instead of re-implementing.
