Docker Image bauen und veröffentlichen / docker (push) Successful in 20m29s
Switch from a dynamically-derived registry/GITHUB_TOKEN login to the same pattern already proven in the ebooks project: a fixed git.arnef.de/arnef/nidus registry/image, docker/login-action with REGISTRY_USERNAME/REGISTRY_PASSWORD repo secrets, docker/metadata-action for tag/label generation (version, major.minor, latest, short SHA), and a final buildx/system prune cleanup step. Also add a manual workflow_dispatch trigger. Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>