fix(frontend): datalake link falls back to /datalake when URL is localhost
Same pattern as the API_URL fix: NEXT_PUBLIC_DATALAKE_URL defaults to http://localhost:3013/datalake in docker-compose, which breaks in production. Now exports DATALAKE_URL from lib/api.ts that resolves to /datalake (nginx-proxied) when the baked-in value is localhost.
Co-Authored-By: Claude Opus 4.6 (1M context) noreply@anthropic.com