feat(scheduler): each row shows its last three runs, an interrupted run as such, and the ad-hoc runs beside the jobs

A row's one dot said how the LAST run went, and an interrupted run fell through to "idle" — a grey dot
that read as "no run recorded". The row now leads with its last three runs, newest first, each named
for a screen reader and in its tooltip (how it went, when, who started it); an interrupted run is a
ring, set apart from a skipped run and a failure, and its line says the server restarted under it.

A channel's full-history backfill gets its own "Ad-hoc runs" block: its runs, its channel and what
it fetched, no interval and no run button — it needs its target. AD_HOC_JOBS names every such job;
the backend-id contract holds their names in both languages, and run_ad_hoc refuses any other id.

frontend/src/components/Scheduler.menu.dom.test.tsx

@@ -32,9 +32,14 @@ const status = (over: Partial<SchedulerStatus> = {}): SchedulerStatus => ({
       last_result: null,
       result: null,
       last_error: null,
+      last_trigger: null,
+      last_run_id: null,
+      quota_units: null,
+      recent: [],
       progress: null,
     },
   ],
+  ad_hoc: [],
   queue: {
     channels_recent_pending: 0,
     channels_deep_pending: 0,