Fix gateway CI to build and deploy via registry

.gitea/workflows/gateway-build.yml

@@ -39,8 +39,9 @@ jobs:
           echo "Docker context: $(docker context show 2>/dev/null || true)"
           docker info 2>/dev/null | sed -n '/HTTP Proxy:/p;/HTTPS Proxy:/p;/Name:/p'
 
-          if ! docker image inspect "${{ env.BASE_IMAGE }}" >/dev/null 2>&1; then
-            echo "Runtime base image ${{ env.BASE_IMAGE }} is missing; building it now."
+          if ! docker image inspect "${{ env.BASE_IMAGE }}" >/dev/null 2>&1 \
+            || ! docker run --rm "${{ env.BASE_IMAGE }}" sh -lc 'command -v npm >/dev/null'; then
+            echo "Runtime base image ${{ env.BASE_IMAGE }} is missing npm; building it now."
             BASE_IMAGE="${{ env.RUNTIME_BASE_SOURCE_IMAGE }}" \
             RUNTIME_BASE_IMAGE="${{ env.BASE_IMAGE }}" \
             SINGBOX_VERSION="${{ env.SINGBOX_VERSION }}" \