refactor: GPU Infrastruktur aus Core Admin entfernt (liegt im Lehrer)

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

admin-core/lib/navigation.ts

@@ -38,15 +38,6 @@ export const navigation: NavCategory[] = [
     colorClass: 'infrastructure',
     description: 'GPU, Security, CI/CD & Monitoring',
     modules: [
-      {
-        id: 'gpu',
-        name: 'GPU Infrastruktur',
-        href: '/infrastructure/gpu',
-        description: 'vast.ai GPU Management',
-        purpose: 'GPU-Instanzen auf vast.ai fuer ML-Training und Inferenz verwalten.',
-        audience: ['DevOps', 'Entwickler'],
-        subgroup: 'Compute',
-      },
       {
         id: 'middleware',
         name: 'Middleware',