Branch pushes deploy a per-branch staging instance at
tracker-<slug>.home.arpa via the NAS act_runner; branch deletion tears
it down. build.yml ports the GitHub CI workflow so prod image builds
keep running on Gitea now that .gitea/workflows/ exists (Gitea ignores
.github/workflows/ when it does).
Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
