Fix admin login and CORS issues

- Update CORS configuration to allow frontend on port 3005
- Fix auth service to map email field to username for backend compatibility
- Add loading state handling in AdminLayout
- Add error boundary to dashboard route
- Fix unused parameter warning in login function

🤖 Generated with [Claude Code](https://claude.ai/code)

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

docker-compose.local.yml

@@ -11,8 +11,8 @@ services:
       - NODE_ENV=development
       - PORT=3000
       - JWT_SECRET=local-dev-secret-key-123
-      - ADMIN_URL=http://localhost:3001
-      - FRONTEND_URL=http://localhost:3000
+      - ADMIN_URL=http://localhost:3005
+      - FRONTEND_URL=http://localhost:3005
       # Email - uses Mailhog
       - SMTP_HOST=mailhog
       - SMTP_PORT=1025