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/Layout/Sidebar.tsx

@@ -5,6 +5,7 @@ import {
   ClockCircleOutlined,
   CloudServerOutlined,
   ClusterOutlined,
+  CrownOutlined,
   DashboardOutlined,
   DatabaseOutlined,
   FireOutlined,
@@ -70,12 +71,13 @@ const NAV: NavSection[] = [
     labelKey: 'nav.section.system',
     items: [
       { path: '/cluster',  labelKey: 'nav.cluster',  icon: <ApartmentOutlined /> },
+      { path: '/license',  labelKey: 'nav.license',  icon: <CrownOutlined /> },
       { path: '/settings', labelKey: 'nav.settings', icon: <SettingOutlined /> },
     ],
   },
 ]
 
-const VERSION = '1.0.46'
+const VERSION = '1.0.47'
 
 export default function Sidebar({ isOpen, onClose }: SidebarProps) {
   const { t } = useTranslation()