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/Alerts/index.tsx

@@ -12,6 +12,7 @@ import dayjs from 'dayjs'
 
 import apiClient, { isEnvelope } from '../../api/client'
 import PageHeader from '../../components/PageHeader'
+import EmptyState from '../../components/EmptyState'
 
 const { Text } = Typography
 
@@ -234,6 +235,11 @@ export default function AlertsPage() {
 
   const kind = Form.useWatch('kind', form)
 
+  const openChannelCreate = () => {
+    setCreating(true); form.resetFields()
+    form.setFieldsValue({ kind: 'webhook', active: true, smtp_port: 587, use_tls: true })
+  }
+
   return (
     <div>
       <PageHeader
@@ -266,17 +272,25 @@ export default function AlertsPage() {
           children: (
             <Card size="small" extra={
               <Button type="primary" size="small" icon={<PlusOutlined />}
-                onClick={() => {
-                  setCreating(true); form.resetFields()
-                  form.setFieldsValue({ kind: 'webhook', active: true, smtp_port: 587, use_tls: true })
-                }}>
+                onClick={openChannelCreate}>
                 {t('alerts.add')}
               </Button>
             }>
               <Table size="small" rowKey="id" loading={channels.isFetching}
                 dataSource={channels.data ?? []} columns={chanColumns}
                 pagination={false}
-                locale={{ emptyText: t('alerts.emptyChannels') }} />
+                locale={{ emptyText: (
+                  <EmptyState
+                    icon={<BellOutlined />}
+                    title={t('alerts.emptyChannelsTitle')}
+                    description={t('alerts.emptyChannelsDesc')}
+                    action={
+                      <Button type="primary" icon={<PlusOutlined />} onClick={openChannelCreate}>
+                        {t('alerts.add')}
+                      </Button>
+                    }
+                  />
+                ) }} />
             </Card>
           ),
         },
@@ -288,7 +302,13 @@ export default function AlertsPage() {
               <Table size="small" rowKey="id" loading={events.isFetching}
                 dataSource={events.data ?? []} columns={evColumns}
                 pagination={{ pageSize: 25 }}
-                locale={{ emptyText: t('alerts.emptyEvents') }} />
+                locale={{ emptyText: (
+                  <EmptyState
+                    icon={<BellOutlined />}
+                    title={t('alerts.emptyEventsTitle')}
+                    description={t('alerts.emptyEventsDesc')}
+                  />
+                ) }} />
             </Card>
           ),
         },