Adds a `{{major}}` tag so users can pin to `jmap-webmail:1` and receive
non-breaking minor/patch updates without manually bumping the tag each
release.
Closes#57. Thanks @joelpurra.
Automate multi-arch Docker image builds (amd64+arm64) on push to main
or version tags via GitHub Actions. Add OCI metadata labels for GHCR
discoverability. Update release script to sync infra files to
public-release branch.