Deploy `main` to Dev Landscape

[GenosseOtt]

Description

As a developer on openMCP-UI, I want to verify quick fixes and improvements with our colleagues to seek quick feedback.

This is why we should have an image for our main branches in ui-frontend & ui-backend.
The image should be automatically created for every push to ui-frontend main and ui-backend main.
The tags should look like this main-${SHA}.
We also need a cleanup GHA in the repos which deletes the oldest x tags so we keep the ghcr.io clean.

We will use flux to auto update our image using the image-automation-controller https://fluxcd.io/flux/guides/image-update/.

Tasks

• Create gha for creating main docker images
  • ui-frontend
  • ui-backend
• Install flux image-automation-controller in cluster (environments repo)
• Add imagepolicy & imagerepository as well as the imageupdateautomation to the ui environments setup

Acceptance Criteria

• Latest main branch of ui backend + ui frontend is deployed to dev landscape
• deployments are automatically updated in the deployment, if the main image is updated.