Add picpeak/backend + picpeak/frontend on Docker Hub alongside GHCR. The
merge jobs already assemble the multi-arch manifest from the per-arch GHCR
digests via 'imagetools create'; adding Docker Hub to metadata-action's
images list + a Docker Hub login makes the same command push the manifest to
both registries (blobs copied from GHCR). No change to the build-by-digest
jobs.
Full tag parity (main, stable, latest, semver, sha). Gated on
DOCKERHUB_ENABLED (github.repository == PicPeak/picpeak) so forks stay
GHCR-only and keep building. Requires repo secrets DOCKERHUB_USERNAME and
DOCKERHUB_TOKEN.
Luca
1f19fbb1b2