Caddy routes /api/* and /webhooks/* to 172.20.1.238:3002 but the
docker-compose had PORT=3001 and bound port 3001. Changed:
- PORT env var: 3001 -> 3002
- Port binding: 0.0.0.0:3002:3002
- Health check: localhost:3002/health
- Next.js rewrites: localhost:3001 -> localhost:3002
- Frontend port: 127.0.0.1 -> 0.0.0.0 (Caddy remote access)