Fix frontend staging healthcheck for locale redirect

Accept 2xx/3xx on / so next-intl redirect to /en no longer marks the
container unhealthy and blocks nginx from starting.

Co-authored-by: Cursor <cursoragent@cursor.com>

frontend/Dockerfile

@@ -53,7 +53,7 @@ USER dyolink
 EXPOSE 3000
 
 HEALTHCHECK --interval=30s --timeout=5s --start-period=40s --retries=3 \
-  CMD node -e "require('http').get('http://127.0.0.1:3000/', (r) => {if(r.statusCode!==200)process.exit(1)})"
+  CMD node -e "require('http').get('http://127.0.0.1:3000/', (r) => { process.exit(r.statusCode >= 200 && r.statusCode < 400 ? 0 : 1); }).on('error', () => process.exit(1))"
 
 ENTRYPOINT ["dumb-init", "--", "docker-entrypoint.sh"]