Update to Keycloak 26

- Use `persistent-user-sessions:v1,hostname:v2` [Keycloak features](https://www.keycloak.org/server/features)
- Use `/opt/keycloak/data/import` to import realm

Waiting for bitnami to support Keycloak 26: https://hub.docker.com/r/bitnami/keycloak/tags