feat(dashboard): HAProxy Listener-Stats + i18n-Relativzeit

- haproxy_stats.go: FRONTEND-Rows aus show-stat CSV auslesen und als
  frontends[] zurückgeben (Name, Sessions, MaxSess, Bytes, ReqTot/Rate)
- Dashboard: Listener-Sektion über Backend-Liste; query jetzt unified
  haproxyStats mit backends/frontends alias für Abwärtskompatibilität
- common.relTime.*-Keys (en+de) eingeführt; relativeTime/relativeFromIso
  in Dashboard + relTime in WireGuard Servers/Clients auf t-Parameter
  umgestellt statt hardcodierter Strings
- CertExpiry in Cluster-Seite nutzt jetzt certDaysRemaining/certExpiredDaysAgo

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

management-ui/src/i18n/locales/de/common.json

@@ -757,7 +757,8 @@
     },
     "haproxyCard": {
       "title": "HAProxy-Backends (live)",
-      "empty": "Keine Backend-Stats erreichbar (HAProxy down oder admin.sock-permission)."
+      "empty": "Keine Backend-Stats erreichbar (HAProxy down oder admin.sock-permission).",
+      "frontends": "Listener"
     },
     "resCard": {
       "load": "Load",

management-ui/src/i18n/locales/en/common.json

@@ -757,7 +757,8 @@
     },
     "haproxyCard": {
       "title": "HAProxy backends (live)",
-      "empty": "No backend stats reachable (HAProxy down or admin.sock permission)."
+      "empty": "No backend stats reachable (HAProxy down or admin.sock permission).",
+      "frontends": "Listeners"
     },
     "resCard": {
       "load": "Load",

management-ui/src/pages/Dashboard/index.tsx

@@ -104,6 +104,11 @@ interface HAProxyBackend {
   req_tot: number; req_rate: number
   last_change_sec: number; health?: string
 }
+interface HAProxyFrontend {
+  name: string; sessions: number; max_sess: number
+  bytes_in: number; bytes_out: number
+  req_tot: number; req_rate: number
+}
 
 // ── Fetchers ──────────────────────────────────────────────────
 
@@ -189,11 +194,19 @@ export default function DashboardPage() {
     queryFn: () => fetchOne<Resources>('/system/resources'),
     refetchInterval: 10_000,
   })
-  const haproxyBackends = useQuery({
+  const haproxyStats = useQuery({
     queryKey: ['haproxy', 'stats'],
-    queryFn: () => fetchList<HAProxyBackend>('/haproxy/stats', 'backends'),
+    queryFn: async () => {
+      try {
+        const r = await apiClient.get('/haproxy/stats')
+        if (!isEnvelope(r.data)) return { backends: [] as HAProxyBackend[], frontends: [] as HAProxyFrontend[] }
+        const d = r.data.data as { backends?: HAProxyBackend[]; frontends?: HAProxyFrontend[] }
+        return { backends: d.backends ?? [], frontends: d.frontends ?? [] }
+      } catch { return { backends: [] as HAProxyBackend[], frontends: [] as HAProxyFrontend[] } }
+    },
     refetchInterval: 10_000,
   })
+  const haproxyBackends = { data: haproxyStats.data?.backends }
   const auditEntries = useAuditLive(15)
 
   const domains  = useQuery({ queryKey: ['domains'],            queryFn: () => fetchList<Domain>('/domains', 'domains') })
@@ -450,6 +463,27 @@ export default function DashboardPage() {
         {/* ── HAProxy backend live health ─────────────────── */}
         <Col xs={24} lg={12}>
           <Card size="small" title={<><DatabaseOutlined /> {t('dashboard.haproxyCard.title')}</>} className="h-100">
+            {(haproxyStats.data?.frontends ?? []).length > 0 && (
+              <div style={{ marginBottom: 8, paddingBottom: 8, borderBottom: '1px solid #E2E8F0' }}>
+                <Text type="secondary" style={{ fontSize: 10, textTransform: 'uppercase', letterSpacing: 0.5 }}>
+                  {t('dashboard.haproxyCard.frontends')}
+                </Text>
+                <Space direction="vertical" size={2} style={{ width: '100%', marginTop: 4 }}>
+                  {(haproxyStats.data?.frontends ?? []).map((f) => (
+                    <div key={f.name} style={{ fontSize: 12, color: '#334155' }}>
+                      <Space size={6} wrap>
+                        <code style={{ fontSize: 11 }}>{f.name}</code>
+                        <Text type="secondary" style={{ fontSize: 11 }}>
+                          {f.sessions} sess
+                          {f.req_rate > 0 ? ` · ${f.req_rate}/s` : ''}
+                          {` · ↓${formatBytes(f.bytes_in)} ↑${formatBytes(f.bytes_out)}`}
+                        </Text>
+                      </Space>
+                    </div>
+                  ))}
+                </Space>
+              </div>
+            )}
             {(haproxyBackends.data ?? []).length === 0 ? (
               <Text type="secondary">{t('dashboard.haproxyCard.empty')}</Text>
             ) : (