docker/build-push-action@v6 renamed the parameter from 'dockerfile' to
'file'. The backend succeeded by luck (default Dockerfile matched), but
nginx failed because the Dockerfile isn't in the root context directory.
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
Adds a GitHub Actions workflow that builds and pushes backend and nginx
images to GitHub Container Registry on every merge to main and on
releases. Adds docker-compose.ghcr.yml for end users who want to deploy
without cloning the repo, and updates the README with Quick Deploy
instructions alongside the existing build-from-source guide.
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>