Add QEMU setup and multi-platform build to the Docker workflow so
the image is published with both linux/amd64 and linux/arm64
support, enabling native execution on Apple Silicon and other
ARM64 hosts.
Set the CLI build version from OBSCURA_VERSION, GitHub tag refs, or Cargo.toml fallback. Use that same build version for both --version and the startup banner, and pass the Docker tag version into Docker builds.
Adds a workflow that triggers on v* tag pushes and:
- Logs into Docker Hub using DOCKERHUB_USERNAME + DOCKERHUB_TOKEN secrets
- Builds the image from the existing Dockerfile
- Tags it with both the version (e.g. 0.1.4) and 'latest'
- Pushes both tags
GitHub Actions cache is used for layers to speed up subsequent builds.
