chore(deps)!: Upgrade to Keycloak 26

[fhennig]

resolves #1221

preview URL: https://keycloak26.loculus.org

Summary

• Created copying @corneliusroemer's KC26 PR Switch keycloakify PR to use Keycloak 26 #3275
• Switching out CLI args for ENV vars

Explanation of breaking changes

It's marked breaking to draw attention to the fact that this is hard to roll back:

Back up the database using instructions in the documentation for your relational database. The database will no longer be compatible with the old server after you upgrade the server. If you need to revert the upgrade, first restore the old installation, and then restore the database from the backup copy.

https://www.keycloak.org/docs/latest/upgrading/

[corneliusroemer]

@fhennig I cleaned up history to show original authorship and added wrote the PR message