Add i18n, branding, user management, health checks, and cleanup for deployment

- Multi-language support (EN/DE) with i18n engine and language files
- Configurable branding (name, subtitle, logo) in Settings
- Global default language and per-user language preference
- User management router with CRUD endpoints
- Customer status sync on start/stop/restart
- Health check fixes: derive status from container state, remove broken wget healthcheck
- Caddy reverse proxy and dashboard env templates for customer stacks
- Updated README with real hardware specs, prerequisites, and new features
- Removed .claude settings (JWT tokens) and build artifacts from tracking
- Updated .gitignore for .claude/ and Windows artifacts

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

templates/dashboard.env.j2

@@ -0,0 +1,13 @@
+# NetBird Dashboard - Customer {{ customer_id }}
+NETBIRD_MGMT_API_ENDPOINT={{ external_url }}
+NETBIRD_MGMT_GRPC_API_ENDPOINT={{ external_url }}
+AUTH_AUTHORITY={{ external_url }}/oauth2
+AUTH_CLIENT_ID=netbird-dashboard
+AUTH_AUDIENCE=netbird-dashboard
+AUTH_SUPPORTED_SCOPES=openid profile email groups offline_access
+AUTH_REDIRECT_URI=/nb-auth
+AUTH_SILENT_REDIRECT_URI=/nb-silent-auth
+USE_AUTH0=false
+NETBIRD_TOKEN_SOURCE=accessToken
+LETSENCRYPT_DOMAIN=none
+NGINX_SSL_PORT=443