fix(ci): lowercase GHCR owner tags and harden frontend runtime image

.github/workflows/cdn-latest.yml

@@ -34,9 +34,12 @@ jobs:
       - name: Set up Docker Buildx
         uses: docker/setup-buildx-action@v3
 
-      - name: set lower case owner name
+      - name: Set lower case owner name
+        id: repo_owner
         run: |
-          echo "REPO_OWNER=${OWNER,,}" >>${GITHUB_ENV}
+          LOWER_OWNER="${OWNER,,}"
+          echo "REPO_OWNER=${LOWER_OWNER}" >>"$GITHUB_ENV"
+          echo "repo_owner=${LOWER_OWNER}" >>"$GITHUB_OUTPUT"
         env:
           OWNER: "${{ github.repository_owner }}"