NEXT_DEV_PROFILE=codeserver wires basePath, assetPrefix, and
allowedDevOrigins from CODESERVER_HOST/PORT in .env.local. Use
/absproxy/{port} so code-server preserves the path prefix and Next's
basePath matches the incoming request.
Run with `npm run dev:codeserver` and access via
https://<host>/absproxy/<port>/.
