fixed step output

.gitea/workflows/publish-docker.yaml

@@ -38,7 +38,9 @@ jobs:
           else
             IMAGE_TAG="latest"
           fi
-          echo "image_tag=${IMAGE_TAG}"
+          echo "Identified IMAGE_TAG=${IMAGE_TAG}"
+          # Store the resolved image tag as an output for subsequent steps
+          echo "image_tag=${IMAGE_TAG}" >> "$GITHUB_OUTPUT"
 
       - name: Build and push docker image
         uses: docker/build-push-action@v5