Adds a workflow that triggers on push to main: builds backend/frontend Docker images, pushes to Gitea container registry, pulls and restarts on the host, health checks, prunes old images, and sends ntfy notifications. docker-compose.yaml updated to pull pre-built images from registry and includes act_runner as a 4th service. Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>