Fix Flood 4.7 Node runtime compatibility and gate publishing on startup

Dockerfile.client

@@ -2,7 +2,7 @@
 # Build from a clean upstream release checkout using the Gitea workflow.
 
 ARG BUILDPLATFORM=amd64
-ARG NODE_IMAGE=docker.io/node:24-alpine3.24
+ARG NODE_IMAGE=docker.io/node:22-alpine3.24
 
 FROM --platform=$BUILDPLATFORM ${NODE_IMAGE} as nodebuild
 
@@ -48,5 +48,8 @@ RUN apk add coreutils
 # System local configuration
 VOLUME /server/db/
 
+# Fail the build before publication if the actual server cannot start.
+RUN node .ci-startup.cjs && rm .ci-startup.cjs
+
 # Flood server in development mode
 ENTRYPOINT ["npm", "--prefix=/usr/src/app/", "run", "start:development:server", "--", "--host=0.0.0.0", "--rundir=/server/"]