#783 added `type=semver,pattern=v{{version}}` to the merge-job metadata,
but metadata-action silently dropped it on prereleases — the 3.84.0-beta.0
build published only :3.84.0-beta.0 + :sha, not :v3.84.0-beta.0 (verified
in the merge-backend push log + GHCR: :v3.84.0-beta.0 → 404).
Replace the v{{version}}/v{{major}} semver patterns with type=ref,event=tag,
which emits the git-tag name verbatim (v3.45.0 / v3.84.0-beta.0) for both
stable and beta tags — exactly the string users pin (matches the GitHub
release). Applies to both backend + frontend merge metadata steps.
Takes effect on the next release build. The bare :3.84.0-beta.0 tags stay
(the {{version}} patterns are unchanged), so both forms resolve.