feat(dashboards): 1600px max-width, richer Downloads filters, needs-attention + sticky headers

Operator-flagged 2026-05-28: the Subscriptions/Downloads dashboards were
full-bleed and thin on filtering. Chosen via AskUserQuestion.

**Layout**
- SubscriptionsView capped at a centered max-width 1600px (covers all
  three subtabs) so rows aren't a mile wide on ultrawide monitors.
- Sticky control headers on both tabs (top: 48px, below the top nav,
  opaque bg) so filters/stat-chips stay reachable while scrolling a
  long list.

**Downloads filters (all four requested)**
- Stat chips are now clickable filters: click Queued/Running/Completed/
  Failed/Skipped to filter the list to that status; the active chip is
  outlined + elevated; re-click clears.
- Free-text search box over the loaded events (artist / platform /
  error substring).
- Artist filter: the filter popover's numeric "Source ID" field is
  replaced with an artist autocomplete (sources.autocompleteArtist →
  artist_id, which /api/downloads already supports). Pill shows the
  artist name.
- "Show no-change scans" toggle (default OFF): hides status=ok/skipped
  rows with 0 files (the scheduled scans that found nothing) so real
  downloads + failures stand out.

**Subscriptions**
- "Needs attention" quick-filter chip: one click to show only artists
  with sources that have errors OR have never been checked; chip shows
  the count and disables the status dropdown while active.

Frontend-only — backend filter params (status/artist_id/date) and the
/api/downloads endpoint already supported everything.

frontend/src/components/subscriptions/DownloadsTab.vue

@@ -1,20 +1,41 @@
 <template>
   <div>
-    <div class="fc-dl__top">
-      <DownloadStatChips :stats="store.stats" />
-      <span v-if="liveActive" class="fc-dl__live" title="Auto-refreshing while downloads are active">
-        <span class="fc-dl__live-dot" />
-        live
-      </span>
-      <v-spacer />
-      <v-btn variant="text" icon @click="refresh">
-        <v-icon>mdi-refresh</v-icon>
-        <v-tooltip activator="parent" location="top">Refresh</v-tooltip>
-      </v-btn>
-      <MaintenanceMenu @refresh="refresh" />
-    </div>
+    <div class="fc-dl__sticky">
+      <div class="fc-dl__top">
+        <DownloadStatChips
+          :stats="store.stats"
+          :active-status="filterModel.status"
+          @select="onStatusChipSelect"
+        />
+        <span v-if="liveActive" class="fc-dl__live" title="Auto-refreshing while downloads are active">
+          <span class="fc-dl__live-dot" />
+          live
+        </span>
+        <v-spacer />
+        <v-btn variant="text" icon @click="refresh">
+          <v-icon>mdi-refresh</v-icon>
+          <v-tooltip activator="parent" location="top">Refresh</v-tooltip>
+        </v-btn>
+        <MaintenanceMenu @refresh="refresh" />
+      </div>
 
-    <DownloadsFilterPopover v-model="filterModel" class="fc-dl__filter" />
+      <div class="fc-dl__controls">
+        <v-text-field
+          v-model="search"
+          density="compact" variant="outlined" hide-details clearable
+          prepend-inner-icon="mdi-magnify"
+          placeholder="Search artist / platform / error"
+          style="max-width: 340px"
+        />
+        <DownloadsFilterPopover v-model="filterModel" />
+        <v-switch
+          v-model="showNoChange"
+          label="Show no-change scans"
+          density="compact" hide-details color="accent"
+          class="fc-dl__nochange"
+        />
+      </div>
+    </div>
 
     <v-alert v-if="store.error" type="error" variant="tonal" closable class="my-4">
       {{ String(store.error) }}
@@ -92,6 +113,17 @@ const route = useRoute()
 const store = useDownloadsStore()
 const filterModel = ref({ ...store.filter })
 
+// Free-text search (client-side over the loaded events) + a toggle to
+// hide "no-change" scheduled scans (status=ok/skipped with 0 files) so
+// real downloads + failures stand out. Operator-flagged 2026-05-28.
+const search = ref('')
+const showNoChange = ref(false)
+
+// Clicking a stat chip toggles a status filter (re-click clears it).
+function onStatusChipSelect(statusKey) {
+  filterModel.value = { ...filterModel.value, status: statusKey }
+}
+
 // Each group's collapsed state persists across refreshes for the
 // lifetime of the SubscriptionsView (operator-friendly default: all
 // expanded; collapse what you don't care about right now).
@@ -158,6 +190,21 @@ const filteredEvents = computed(() => {
     const toTs = new Date(to).getTime() + 24 * 3600 * 1000 - 1
     arr = arr.filter((e) => new Date(e.started_at).getTime() <= toTs)
   }
+  // Hide no-change scheduled scans (succeeded/skipped, downloaded
+  // nothing) unless the operator opts to show them.
+  if (!showNoChange.value) {
+    arr = arr.filter(
+      (e) => !((e.status === 'ok' || e.status === 'skipped') && !(e.files_count > 0)),
+    )
+  }
+  const q = search.value?.trim().toLowerCase()
+  if (q) {
+    arr = arr.filter((e) =>
+      (e.artist_name || '').toLowerCase().includes(q)
+      || (e.platform || '').toLowerCase().includes(q)
+      || (e.error || '').toLowerCase().includes(q),
+    )
+  }
   return arr
 })
 
@@ -207,6 +254,7 @@ watch(filterModel, async (m) => {
   await store.applyFilter({
     status: m.status,
     source_id: m.source_id || null,
+    artist_id: m.artist_id || null,
     from_date: m.from_date,
     to_date: m.to_date,
   })
@@ -219,12 +267,27 @@ async function openDetail(id) {
 </script>
 
 <style scoped>
+/* Sticky control header: stat chips + search + filter + toggle stay
+   pinned below the top nav while the event feed scrolls. Opaque
+   background so rows don't bleed through. */
+.fc-dl__sticky {
+  position: sticky;
+  top: 48px;
+  z-index: 3;
+  background: rgb(var(--v-theme-background));
+  padding: 8px 0 10px;
+  margin-bottom: 4px;
+  border-bottom: 1px solid rgb(var(--v-theme-on-surface-variant) / 0.12);
+}
 .fc-dl__top {
   display: flex; gap: 8px; align-items: center;
-  margin-bottom: 12px;
+  margin-bottom: 10px;
   flex-wrap: wrap;
 }
-.fc-dl__filter { margin-bottom: 12px; }
+.fc-dl__controls {
+  display: flex; gap: 12px; align-items: center; flex-wrap: wrap;
+}
+.fc-dl__nochange { flex: 0 0 auto; }
 .fc-dl__live {
   display: inline-flex; align-items: center; gap: 5px;
   font-size: 0.72rem; text-transform: uppercase; letter-spacing: 0.06em;