fix: use registry hostname as auth key, include owner in REGISTRY_URL

.gitea/workflows/build.yml

@@ -117,7 +117,9 @@ jobs:
           # the Podman daemon which correctly uses HTTP (insecure=true in registries.conf).
           mkdir -p ~/.docker
           AUTH=$(echo -n "${{ secrets.REGISTRY_USERNAME }}:${{ secrets.REGISTRY_PASSWORD }}" | base64 -w 0)
-          echo "{\"auths\":{\"${{ env.REGISTRY }}\":{\"auth\":\"${AUTH}\"}}}" > ~/.docker/config.json
+          # Auth key must be the registry hostname only (e.g. host:port), not the full path
+          REGISTRY_HOST=$(echo "${{ env.REGISTRY }}" | cut -d'/' -f1)
+          echo "{\"auths\":{\"${REGISTRY_HOST}\":{\"auth\":\"${AUTH}\"}}}" > ~/.docker/config.json
           docker push "${{ steps.image.outputs.full }}"
 
       - name: Save image to file