- Makefile: add IMAGE_REGISTRY/IMAGE_REPO/IMAGE_TAG vars + image, push, image-tag targets
- .gitea/workflows/image.yaml: build+push on main push and v* tags via metadata-action
- README: Container Image section with pull/build/push/CI secret docs
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>