Server releases include the changelog and a link to the GHCR package

The release workflow now writes the release body to a file (release-body.md) instead of passing multi-line notes through GitHub Actions outputs, which prevents the notes from being lost when jobs are re-run. The body also includes a clickable link to the GHCR package page so users can browse published image versions. The same file-based approach is used for Helm chart releases. Sources: https://github.com/tuist/hive/commit/4431deb