feat(license): Lizenz-System mit Ed25519-Verify gegen license.netcell-it.com

Portiert mail-gateway/internal/license (Verify, Cache, Trial, Signature)
+ DB-Mirror (internal/services/license) + REST-Handler (status/verify/key/clear)
+ UI-Page /license (Activate, Status, Limits, Features, Re-verify)
+ <LicenseBanner /> neben UpdateBanner (trial-expiring, expired, verify-failed)
+ Scheduler: täglich Re-verify (24h-Tick)

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

management-ui/src/components/LicenseBanner.tsx

@@ -0,0 +1,91 @@
+import { Alert } from 'antd'
+import { Link } from 'react-router-dom'
+import { useQuery } from '@tanstack/react-query'
+import { useTranslation } from 'react-i18next'
+
+import apiClient, { isEnvelope } from '../api/client'
+
+interface LicenseStatus {
+  license_key?: string
+  status: string
+  type?: string
+  valid_until?: string
+  expires_at?: string
+  last_error?: string | null
+}
+
+// LicenseBanner shows up in AppLayout next to UpdateBanner.
+// Three visible states:
+//  - trial-expiring (≤14d remaining) → warning
+//  - expired / invalid → error
+//  - last verify failed → warning (transient)
+// Everything else stays silent.
+export default function LicenseBanner() {
+  const { t } = useTranslation()
+
+  const { data: s } = useQuery({
+    queryKey: ['license', 'status'],
+    queryFn: async () => {
+      const r = await apiClient.get('/license/status')
+      return isEnvelope(r.data) ? (r.data.data as LicenseStatus) : null
+    },
+    refetchInterval: 5 * 60 * 1000,
+  })
+
+  if (!s) return null
+
+  const expiry = s.valid_until || s.expires_at
+  const days = expiry ? Math.ceil((new Date(expiry).getTime() - Date.now()) / 86_400_000) : null
+  const isTrial = s.type === 'trial' || !s.license_key
+
+  if (s.status === 'expired' || s.status === 'invalid') {
+    return (
+      <Alert
+        type="error"
+        showIcon
+        banner
+        message={
+          <>
+            {t('licenseBanner.expired')}{' '}
+            <Link to="/license">{t('licenseBanner.cta')}</Link>
+          </>
+        }
+      />
+    )
+  }
+
+  if (isTrial && days !== null && days <= 14) {
+    return (
+      <Alert
+        type={days <= 3 ? 'error' : 'warning'}
+        showIcon
+        banner
+        message={
+          <>
+            {t('licenseBanner.trialExpiring', { days })}{' '}
+            <Link to="/license">{t('licenseBanner.cta')}</Link>
+          </>
+        }
+      />
+    )
+  }
+
+  if (s.last_error) {
+    return (
+      <Alert
+        type="warning"
+        showIcon
+        banner
+        message={
+          <>
+            {t('licenseBanner.verifyFailed')}: {s.last_error}{' '}
+            <Link to="/license">{t('licenseBanner.openPage')}</Link>
+          </>
+        }
+        closable
+      />
+    )
+  }
+
+  return null
+}