Release / build-and-push (push) Failing after 3m56s
Adds .gitea/workflows/release.yml. On a v* git tag push (or manual dispatch), builds the Dockerfile and publishes to git.linuxhg.com/bookhoard/bookhoard under two tags: the version (${{ gitea.ref_name }}) and 'latest'. Auth uses the auto-provided GITHUB_TOKEN; no secret to manage. Pushes to main do nothing, so work-in-progress commits never ship.