backend: require confirmation for signed channel updates [CI]

ci/index-backend-image.sh

@@ -53,3 +53,8 @@ put_tag "$version"
 if [[ "$version" != *-* ]]; then
   put_tag latest
 fi
+
+root="$(cd "$(dirname "${BASH_SOURCE[0]}")/.." && pwd)"
+backend_manifest="$(manifest_head "$version")"
+read -r backend_digest _ _ <<< "$backend_manifest"
+bash "$root/ci/publish-release-offer.sh" backend "$registry/$image" "$backend_digest" "$CI_COMMIT_TAG" release "$root/.release/backend-release"