feat: umfangreiches UI+API-Polish (v1.1.36–1.1.42)

Backend:
- Audit-Log: Search-Endpoint mit ILIKE-Filter (actor/action/subject/date)
- NTP: /ntp/status via chronyc tracking (Stratum, Offset, Quelle)
- System: /service-restart mit Allowlist (haproxy/squid/unbound/chrony/scheduler)
- Domain-Response-Headers + Rate-Limit (Migration 0024)
- Join-Tokens (Migration 0025), Cluster-mTLS, Aggregator-Fan-Out
- apt-Service für Update-Banner (apt-get update + Versionsprüfung)
- Backup-Retry mit exponential backoff (retry_apt 3×)
- publish.sh fail-fast + cleanup-old.sh (max 10 Versionen)

Frontend:
- Audit-Log-Page (/audit) mit Filter + Pagination
- ErrorBoundary an React-Root + Vite build-target festgenagelt (iOS 15+)
- Storage-Schema-Stamp: auto-wipe bei Versions-Mismatch (blank-page-Fix)
- EmptyState-Komponente überall ausgerollt
- SSL: Aggregate-Karte (total/expiring/expired/errors)
- Backups: Aggregate-Karte (letzter Backup/Größe/Fehlschläge 24h) + Backup-Now
- NTP: Sync-Status-Karte (chronyc tracking live)
- Domains: Backend-UP/DOWN-Chip aus HAProxy-Stats
- Backends: HAProxy-Status-Spalte (UP/DEGRADED/DOWN)
- Settings: Service-Neustart-Karte (haproxy/squid/unbound/chrony/scheduler)
- Settings: Upgrade-Status-Card, Wartungsmodus, Auto-Update, Retention
- Dashboard: Recent-Alerts, Cluster-Health, License-Chip, Onboarding-Hint
- System-Regeln im Firewall als eigener Tab

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

management-ui/src/App.tsx

@@ -28,6 +28,7 @@ const NTPPage = lazy(() => import('./pages/NTP'))
 const ClusterPage = lazy(() => import('./pages/Cluster'))
 const FirewallLivePage = lazy(() => import('./pages/FirewallLive'))
 const LogsPage = lazy(() => import('./pages/Logs'))
+const AuditPage = lazy(() => import('./pages/Audit'))
 const BackupsPage = lazy(() => import('./pages/Backups'))
 const DiagnosticsPage = lazy(() => import('./pages/Diagnostics'))
 const AlertsPage = lazy(() => import('./pages/Alerts'))
@@ -118,6 +119,7 @@ export default function App() {
                 <Route path="/ntp" element={<NTPPage />} />
                   <Route path="/cluster" element={<ClusterPage />} />
                   <Route path="/logs" element={<LogsPage />} />
+                  <Route path="/audit" element={<AuditPage />} />
                   <Route path="/backups" element={<BackupsPage />} />
                   <Route path="/diagnostics" element={<DiagnosticsPage />} />
                   <Route path="/alerts" element={<AlertsPage />} />