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/pages/Backends/index.tsx

@@ -8,6 +8,7 @@ import { DatabaseOutlined, PlusOutlined } from '@ant-design/icons'
 import { useMutation, useQuery, useQueryClient } from '@tanstack/react-query'
 import { useTranslation } from 'react-i18next'
 import DataTable from '../../components/DataTable'
+import EmptyState from '../../components/EmptyState'
 import PageHeader from '../../components/PageHeader'
 import ActionButtons from '../../components/ActionButtons'
 import StatusDot from '../../components/StatusDot'
@@ -85,12 +86,37 @@ async function listDomains(): Promise<DomainFull[]> {
   return (r.data.data as { domains?: DomainFull[] }).domains ?? []
 }
 
+interface HAProxyStat { backend: string; server: string; status: string }
+async function listHAProxyStats(): Promise<HAProxyStat[]> {
+  try {
+    const r = await apiClient.get('/haproxy/stats')
+    if (!isEnvelope(r.data)) return []
+    return (r.data.data as { backends?: HAProxyStat[] }).backends ?? []
+  } catch { return [] }
+}
+
 export default function BackendsPage() {
   const { t } = useTranslation()
   const qc = useQueryClient()
 
   const { data, isLoading } = useQuery({ queryKey: ['backends'], queryFn: listBackends })
   const { data: domains } = useQuery({ queryKey: ['domains'], queryFn: listDomains })
+  const { data: haproxyStats } = useQuery({
+    queryKey: ['haproxy', 'stats'],
+    queryFn: listHAProxyStats,
+    refetchInterval: 15_000,
+  })
+
+  // UP = alle Server UP, DEGRADED = mind. 1 UP + mind. 1 DOWN, DOWN = alle DOWN
+  const backendLiveStatus = (id: number): 'UP' | 'DEGRADED' | 'DOWN' | null => {
+    if (!haproxyStats?.length) return null
+    const servers = haproxyStats.filter(s => s.backend === `eg_backend_${id}`)
+    if (!servers.length) return null
+    const upCount = servers.filter(s => s.status === 'UP').length
+    if (upCount === servers.length) return 'UP'
+    if (upCount > 0) return 'DEGRADED'
+    return 'DOWN'
+  }
 
   // server-counts pro Backend laden wir lazy bei Expansion; in der
   // Tabelle reicht ein Hinweis ob 0 / N Server.
@@ -211,6 +237,15 @@ export default function BackendsPage() {
         return <Space size={4} wrap>{ds.map(d => <Tag key={d.id} color="blue">{d.name}</Tag>)}</Space>
       },
     },
+    {
+      title: t('backends.liveStatus'), key: 'liveStatus', width: 110,
+      render: (_, row) => {
+        const s = backendLiveStatus(row.id)
+        if (!s) return <Text type="secondary" style={{ fontSize: 12 }}>—</Text>
+        const color = s === 'UP' ? 'green' : s === 'DEGRADED' ? 'orange' : 'red'
+        return <Tag color={color} style={{ margin: 0 }}>{s}</Tag>
+      },
+    },
     { title: t('backends.active'), dataIndex: 'active', key: 'active', render: (v: boolean) => <StatusDot active={v} /> },
     {
       title: t('common.actions'), key: 'actions',
@@ -235,6 +270,11 @@ export default function BackendsPage() {
     },
   ]
 
+  const openCreate = () => {
+    setCreating(true); form.resetFields()
+    form.setFieldsValue({ scheme: 'http', lb_algorithm: 'roundrobin', websocket: false, active: true })
+  }
+
   return (
     <div>
       <PageHeader
@@ -252,13 +292,22 @@ export default function BackendsPage() {
           rowExpandable: (record) => !!record.id,
         }}
         extraActions={
-          <Button type="primary" icon={<PlusOutlined />} onClick={() => {
-            setCreating(true); form.resetFields()
-            form.setFieldsValue({ scheme: 'http', lb_algorithm: 'roundrobin', websocket: false, active: true })
-          }}>
+          <Button type="primary" icon={<PlusOutlined />} onClick={openCreate}>
             {t('backends.addBackend')}
           </Button>
         }
+        emptyContent={
+          <EmptyState
+            icon={<DatabaseOutlined />}
+            title={t('backends.emptyTitle')}
+            description={t('backends.emptyDesc')}
+            action={
+              <Button type="primary" icon={<PlusOutlined />} onClick={openCreate}>
+                {t('backends.addBackend')}
+              </Button>
+            }
+          />
+        }
       />
       <Modal
         title={editing ? t('backends.editBackend') : t('backends.addBackend')}