Add admin panel API with CRUD for apps

- Express.js backend with JWT authentication
- CRUD endpoints for apps management
- Health check endpoint
- Dockerfile per admin API (Node 18 Alpine)
- Kubernetes: admin-api deployment, service, ingress
- Admin panel at http://admin.apps.local
- Updated nginx.conf to route /api to admin API
- Fixed ingress rules for separate web and admin services

backend/data/apps.json

@@ -0,0 +1 @@
+[]