Switch to GITEA_OUTPUT and transition Docker caching from type=gha to type=registry to better support the Gitea Actions environment. The runner is also pinned to ubuntu-24.04 for consistency.
Introduce a multi-stage Dockerfile, docker-compose setup, and a Gitea Actions workflow to automate building and pushing images to the registry. The configuration includes an entrypoint script for persistent logging and a .dockerignore to optimize the build context.
