Add Keycloak authentication for ETL users.
Configure ETL routes and login/logout functionality.
Integrate ETL with Keycloak SSO.
Update vite.config.js to include etl.js.
Create EtlController with home, login, and logout routes.
Implement EtlAuthenticator for email/password login.
Configure security.yaml for ETL firewall and providers.
Add etl.js and etl.scss for ETL frontend.
Add Keycloak client configuration for ETL.
Update PrestaireController to use absolute URL for login.
