fix: Uppercase not allowed in image name

.gitea/workflows/docker.yaml

@@ -15,7 +15,7 @@ on:
         value: ${{ jobs.build.outputs.images }}
 
 env:
-  OCI_REPO: git.huizinga.dev/${{ gitea.repository_owner}}/${{gitea.event.repository.name}}
+  OCI_REPO_INITIAL: git.huizinga.dev/${{ gitea.repository_owner}}/${{gitea.event.repository.name}}
 
 jobs:
   build:
@@ -27,10 +27,11 @@ jobs:
       - name: Checkout
         uses: actions/checkout@v4
 
-      - name: Set timestamp and release version
+      - name: Setup env
         run: |
           git fetch --prune --unshallow --tags --force
           echo "RELEASE_VERSION=$(git describe --always --dirty='--modified')" >> $GITHUB_ENV
+          echo "OCI_REPO=${OCI_REPO_INITIAL,,}" >>${GITHUB_ENV}
 
       - name: Login to registry
         uses: docker/login-action@v3