Airflow 3.0+ auth updates

[ividito]

Airflow 3.0 reworks auth significantly. There are simple upgrade paths to carry our existing webserver functionality over to Airflow 3+ (maintaining keycloak functionality). A stretch goal here could be to investigate and implement new auth integrations, such as the new Airflow/Keycloak provider.

AC

• Auth configuration updated to be Airflow 3-compatible
• Keycloak provider evaluated (either implemented or documented in a new issue for later)