fix(downloads): rewire MaintenanceMenu to the downloads pipeline

The maintenance dropdown in Subscriptions → Downloads was wired to the
filesystem-import pipeline (POST /api/import/retry-failed +
POST /api/import/clear-stuck) — the subtitles even said so ("Re-enqueue
every failed import task"), but it was contextually misplaced. From the
Downloads view "Retry failed" queued nothing the operator could see
because the action operated on import_task rows, not download_event
rows. Import-pipeline maintenance is already reachable from Settings →
Imports (ImportTaskList.vue), so removing the import wiring loses
nothing.

Rewired:
- "Retry failed" → bulk-retries the failing-sources list, same loop as
  FailingSourcesCard's RETRY ALL (sourcesStore.checkNow per source).
  Subtitle now matches: "Re-queue every currently failing source".
- "Force recovery sweep" → triggers recover_stalled_download_events on
  demand via a new POST /api/downloads/recover-stalled endpoint. The
  sweep also runs every 5 min on Beat; this is the manual fallback so
  the operator doesn't have to wait for the next tick to clear newly
  stranded events.

MaintenanceMenu is now stateless — emits retry-failed and recover-
stalled. DownloadsTab owns the handlers (reuses the existing
onRetryAll; new onRecoverStalled with a delayed refresh so swept rows
land in the failing rollup).

Operator-flagged 2026-05-29 — "the retry failed button in the
maintenance dropdown doesn't appear to queue anything but manual
requeues works."

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

frontend/src/components/subscriptions/MaintenanceMenu.vue

@@ -9,14 +9,14 @@
       <v-list-item
         prepend-icon="mdi-refresh"
         title="Retry failed"
-        subtitle="Re-enqueue every failed import task"
-        @click="onRetry"
+        subtitle="Re-queue every currently failing source"
+        @click="emit('retry-failed')"
       />
       <v-list-item
         prepend-icon="mdi-broom"
-        title="Clear stuck"
-        subtitle="Mark long-running import tasks failed and finalize their batch"
-        @click="onClear"
+        title="Force recovery sweep"
+        subtitle="Mark stranded pending/running events as error (also runs every 5 min)"
+        @click="emit('recover-stalled')"
       />
       <v-list-item
         :disabled="true"
@@ -31,33 +31,9 @@
 </template>
 
 <script setup>
-import { toast } from '../../utils/toast.js'
-import { useImportStore } from '../../stores/import.js'
-
-const emit = defineEmits(['refresh'])
-const importStore = useImportStore()
-
-async function onRetry() {
-  try {
-    await importStore.retryFailed()
-    toast({ text: 'Retry queued', type: 'success' })
-    emit('refresh')
-  } catch (e) {
-    toast({ text: `Retry failed: ${e?.detail || e?.message || e}`, type: 'error' })
-  }
-}
-
-async function onClear() {
-  try {
-    const body = await importStore.clearStuck()
-    const n = body?.cleared ?? 0
-    toast({
-      text: n ? `Cleared ${n} stuck task${n === 1 ? '' : 's'}` : 'Nothing stuck',
-      type: 'success',
-    })
-    emit('refresh')
-  } catch (e) {
-    toast({ text: `Clear failed: ${e?.detail || e?.message || e}`, type: 'error' })
-  }
-}
+// The Downloads tab parent (DownloadsTab.vue) owns the actual retry/sweep
+// handlers — same toast + refresh logic already used by the failing-sources
+// RETRY ALL button. We just emit. Import-pipeline maintenance lives in
+// Settings → Imports (ImportTaskList.vue), not here.
+const emit = defineEmits(['retry-failed', 'recover-stalled'])
 </script>