switch installers and default containers to trixie

@lelutin has already started with the ganeti stuff, i think the next step is fabric and the base-images

• ganeti
  • https://gitlab.com/shared-puppet-modules-group/puppet-ganeti/-/merge_requests/52 -- merged! needs a bump in our Puppetfile
• wiki instructions (e.g. wiki-replica@c97207ab)
• fabric
• base-images

see also switch installers to bookworm (#41244 - closed) previously