feat(db): scheduled DB maintenance — daily targeted VACUUM (ANALYZE)

Adds a daily off-hours VACUUM (ANALYZE) over the high-churn tables the
retention/purge sweeps churn (app_logs, notifications, token tables, notes,
note_versions), on top of Postgres autovacuum, to reclaim bloat left by the
nightly bulk DELETEs and keep planner stats fresh.

- services/db_maintenance.py: run_maintenance() over a closed table allowlist
  via an AUTOCOMMIT connection (VACUUM can't run in a txn); per-table summary
  persisted as the db_maintenance_last_run admin setting.
- services/db_maintenance_scheduler.py: BackgroundScheduler cron (default
  04:00 UTC, after the 03:30 trash purge); enabled-gate checked at fire time;
  live reschedule on hour change. Wired into app.py start/stop.
- routes/admin.py: admin-only GET/PUT /api/admin/db-maintenance + POST /run.
- settings.py: set_admin_setting() (write-side of get_admin_setting) for
  out-of-request writes.
- SettingsView.vue: admin 'Database maintenance' card — enable toggle, run-hour
  (UTC), Run-now, last-run summary.
- Tests: allowlist is closed, VACUUM issued per table, one failure doesn't
  abort the rest, summary persisted; route/scheduler/service surface.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

frontend/src/views/SettingsView.vue

@@ -150,6 +150,16 @@ const serverMarketplaceUrl = ref('');
 const adminMarketplaceUrl = ref('');
 const savingMarketplaceUrl = ref(false);
 const marketplaceUrlSaved = ref(false);
+
+// DB maintenance (admin) — daily targeted VACUUM (ANALYZE).
+interface DbMaintTableResult { table: string; ok: boolean; elapsed_ms: number; error: string | null }
+interface DbMaintRun { started_at: string; elapsed_ms: number; tables: DbMaintTableResult[] }
+const dbMaintEnabled = ref(true);
+const dbMaintHour = ref(4);
+const dbMaintLastRun = ref<DbMaintRun | null>(null);
+const savingDbMaint = ref(false);
+const dbMaintSaved = ref(false);
+const runningDbMaint = ref(false);
 const pluginInstallCommands = computed(() => {
   const mkt = (pluginMarketplaceUrl.value || '').trim()
     || serverMarketplaceUrl.value
@@ -448,6 +458,18 @@ onMounted(async () => {
     // not configured yet
   }
 
+  // DB maintenance config (admin only — endpoint is admin-gated).
+  if (authStore.isAdmin) {
+    try {
+      const dm = await apiGet<{ enabled: boolean; hour: number; last_run: DbMaintRun | null }>("/api/admin/db-maintenance");
+      dbMaintEnabled.value = dm.enabled;
+      dbMaintHour.value = dm.hour;
+      dbMaintLastRun.value = dm.last_run;
+    } catch {
+      // leave defaults
+    }
+  }
+
   // Load admin settings
   if (authStore.isAdmin) {
     try {
@@ -697,6 +719,42 @@ async function saveMarketplaceUrl() {
   }
 }
 
+async function saveDbMaintenance() {
+  savingDbMaint.value = true;
+  dbMaintSaved.value = false;
+  try {
+    await apiPut("/api/admin/db-maintenance", {
+      enabled: dbMaintEnabled.value,
+      hour: dbMaintHour.value,
+    });
+    dbMaintSaved.value = true;
+    setTimeout(() => (dbMaintSaved.value = false), 2000);
+  } catch (e) {
+    const body = (e as { body?: { error?: string } }).body;
+    toastStore.show(body?.error || "Failed to save maintenance settings", "error");
+  } finally {
+    savingDbMaint.value = false;
+  }
+}
+
+async function runDbMaintenanceNow() {
+  runningDbMaint.value = true;
+  try {
+    const summary = await apiPost<DbMaintRun>("/api/admin/db-maintenance/run", {});
+    dbMaintLastRun.value = summary;
+    const failed = summary.tables.filter((t) => !t.ok).length;
+    toastStore.show(
+      failed ? `Maintenance ran with ${failed} error(s)` : "Maintenance complete",
+      failed ? "error" : "success",
+    );
+  } catch (e) {
+    const body = (e as { body?: { error?: string } }).body;
+    toastStore.show(body?.error || "Maintenance run failed", "error");
+  } finally {
+    runningDbMaint.value = false;
+  }
+}
+
 async function handleRestoreFile(event: Event) {
   const file = (event.target as HTMLInputElement).files?.[0];
   if (!file) return;
@@ -1724,6 +1782,51 @@ function formatUserDate(iso: string): string {
         </div>
       </section>
 
+      <section class="settings-section full-width">
+        <h2>Database maintenance</h2>
+        <p class="section-desc">
+          A daily <code>VACUUM (ANALYZE)</code> over the high-churn tables (logs, notifications,
+          tokens, notes, version history) — on top of Postgres autovacuum — to reclaim space left
+          by the nightly cleanup sweeps and keep query plans fresh. Runs at the hour below (UTC),
+          just after trash purge.
+        </p>
+        <div class="checkbox-field">
+          <label>
+            <input type="checkbox" v-model="dbMaintEnabled" />
+            Run scheduled maintenance daily
+          </label>
+        </div>
+        <div class="field url-field">
+          <label for="db-maint-hour">Run hour (UTC)</label>
+          <select id="db-maint-hour" v-model.number="dbMaintHour" class="input">
+            <option v-for="h in 24" :key="h - 1" :value="h - 1">
+              {{ String(h - 1).padStart(2, '0') }}:00
+            </option>
+          </select>
+        </div>
+        <div class="actions">
+          <button class="btn-save" @click="saveDbMaintenance" :disabled="savingDbMaint">
+            {{ savingDbMaint ? "Saving..." : "Save" }}
+          </button>
+          <button class="btn-save btn-secondary" @click="runDbMaintenanceNow" :disabled="runningDbMaint">
+            {{ runningDbMaint ? "Running..." : "Run now" }}
+          </button>
+          <span v-if="dbMaintSaved" class="saved-msg">Saved!</span>
+        </div>
+        <div v-if="dbMaintLastRun" class="db-maint-last">
+          <span class="db-maint-last-label">
+            Last run {{ new Date(dbMaintLastRun.started_at).toLocaleString() }}
+            · {{ dbMaintLastRun.elapsed_ms }}ms
+          </span>
+          <ul class="db-maint-table-list">
+            <li v-for="t in dbMaintLastRun.tables" :key="t.table" :class="{ 'dm-failed': !t.ok }">
+              <code>{{ t.table }}</code>
+              <span class="dm-status">{{ t.ok ? `✓ ${t.elapsed_ms}ms` : `✗ ${t.error}` }}</span>
+            </li>
+          </ul>
+        </div>
+      </section>
+
       <section class="settings-section full-width">
         <h2>Email / SMTP</h2>
         <p class="section-desc">Configure SMTP to enable email notifications for all users.</p>
@@ -2352,6 +2455,32 @@ function formatUserDate(iso: string): string {
 }
 .btn-secondary:hover:not(:disabled) { background: var(--color-action-secondary-hover); }
 .btn-secondary:disabled { opacity: 0.6; cursor: default; }
+
+/* DB maintenance last-run summary */
+.db-maint-last { margin-top: 1rem; }
+.db-maint-last-label {
+  display: block;
+  font-size: 0.8rem;
+  color: var(--color-text-muted);
+  margin-bottom: 0.4rem;
+}
+.db-maint-table-list {
+  list-style: none;
+  margin: 0;
+  padding: 0;
+  display: flex;
+  flex-direction: column;
+  gap: 0.2rem;
+}
+.db-maint-table-list li {
+  display: flex;
+  justify-content: space-between;
+  gap: 1rem;
+  font-size: 0.82rem;
+  padding: 0.2rem 0;
+}
+.db-maint-table-list .dm-status { color: var(--color-text-muted); }
+.db-maint-table-list li.dm-failed .dm-status { color: var(--color-danger); }
 .btn-warn:hover:not(:disabled) {
   background: var(--color-warning);
   color: #fff;