feat(ui): Quick-Toggles, Config-Preview, Dashboard-Alerts, Domain-Detail-Health

Quick-Toggle-Switches (kein Modal nötig) für: Backends, Backend-Server,
DNS-Zonen, DNS-Records, Domains (active), Firewall-Rules, NAT-Rules,
Forward-Proxy ACLs, Routing-Rules.

Dashboard: Alert-Banner für komplett ausgefallene Backends (HAProxy-Stats)
und Domains im Maintenance-Mode.

Domain-Detail: HAProxy-Live-Health-Badge (15s Polling), TLS-Cert
ausstellen/erneuern direkt aus dem Detail, Routing-Rules-Panel inline.

Config-Preview (Settings): alle 4 Generatoren (haproxy, nftables, squid,
unbound) rendern via RenderToString ohne Disk-Write — GET /system/config-preview.

ActionButtons: Viewer-Rolle blendet Delete aus (RBAC-Ergänzung).

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

management-ui/src/pages/Firewall/NATRules.tsx

@@ -81,6 +81,13 @@ export default function NATRulesTab() {
     mutationFn: async (id: number) => { await apiClient.delete(`/firewall/nat-rules/${id}`) },
     onSuccess: () => { void qc.invalidateQueries({ queryKey: ['fw', 'nat'] }) },
   })
+  const quickToggle = useMutation({
+    mutationFn: async ({ id, row, checked }: { id: number; row: NATRule; checked: boolean }) => {
+      await apiClient.put(`/firewall/nat-rules/${id}`, { ...row, enabled: checked })
+    },
+    onSuccess: () => { void qc.invalidateQueries({ queryKey: ['fw', 'nat'] }) },
+    onError: (e: Error) => message.error(e.message),
+  })
 
   const renderTarget = (r: NATRule) => {
     if (r.kind === 'masquerade') return <Tag color="gold">{r.out_zone ?? '?'}-iface IP</Tag>
@@ -105,7 +112,17 @@ export default function NATRulesTab() {
       ),
     },
     { title: t('fw.nat.target'), key: 'target', render: (_, r) => renderTarget(r) },
-    { title: t('fw.nat.enabled'), dataIndex: 'enabled', key: 'enabled', render: (v: boolean) => v ? '✓' : '—' },
+    {
+      title: t('fw.nat.enabled'), dataIndex: 'enabled', key: 'enabled', width: 80,
+      render: (v: boolean, row: NATRule) => (
+        <Switch
+          size="small"
+          checked={v}
+          loading={quickToggle.isPending && quickToggle.variables?.id === row.id}
+          onChange={(checked) => quickToggle.mutate({ id: row.id, row, checked })}
+        />
+      ),
+    },
     {
       title: t('common.edit'), key: 'actions',
       render: (_, row) => (