fix(ci): lowercase image name for registry tag

github.repository preserves the owner's case (jeanGaston), but OCI
registries reject uppercase repository names. Compute a lowercased
IMAGE_NAME env var and use it for both tags instead.

.gitea/workflows/docker-publish.yml

@@ -17,6 +17,9 @@ jobs:
 
       - uses: docker/setup-buildx-action@v3
 
+      - name: Compute lowercase image name
+        run: echo "IMAGE_NAME=$(echo '${{ github.repository }}' | tr '[:upper:]' '[:lower:]')" >> "$GITHUB_ENV"
+
       - name: Log in to Gitea container registry
         uses: docker/login-action@v3
         with:
@@ -30,5 +33,5 @@ jobs:
           context: .
           push: true
           tags: |
-            ${{ vars.REGISTRY_HOST }}/${{ github.repository }}:latest
-            ${{ vars.REGISTRY_HOST }}/${{ github.repository }}:${{ github.sha }}
+            ${{ vars.REGISTRY_HOST }}/${{ env.IMAGE_NAME }}:latest
+            ${{ vars.REGISTRY_HOST }}/${{ env.IMAGE_NAME }}:${{ github.sha }}