Fix docker image lowercasing

[SunkenSplash]

See title.

[Copilot]

Pull request overview

Updates the GitHub Actions release workflow to ensure GHCR image names use a lowercased repository owner, avoiding failures when the owner contains uppercase characters.

Changes:

• Add a per-job step to normalize github.repository_owner to lowercase and expose it via step outputs.
• Update docker metadata/image references and multi-arch manifest creation to use the normalized owner.
• Update digest inspection targets to match the new normalized image paths.

Comments suppressed due to low confidence (1)

.github/workflows/release.yml:300

• These image references are now hardcoded to .../${{ steps.owner.outputs.owner }}/hums-server instead of using the existing env vars (SERVER_IMAGE_NAME/MIGRATE_IMAGE_NAME/WEB_IMAGE_NAME), and those env vars appear to be unused after this change. This increases duplication and makes future renames harder. Consider either removing the unused env vars or setting normalized image name env vars (via $GITHUB_ENV) and using them consistently throughout the workflow (build, manifest, and any documentation steps).

          images: ${{ env.REGISTRY }}/${{ steps.owner.outputs.owner }}/hums-server
          tags: |
            type=raw,value=${{ needs.create-release.outputs.tag }}-${{ matrix.arch }},priority=900
            type=raw,value=v${{ needs.create-release.outputs.version }}-${{ matrix.arch }},priority=850
            type=raw,value=latest-${{ matrix.arch }},priority=600