Add named tunnel mode alongside existing quick tunnel, with systemd
service and setup helper. All tunnel parameters are configurable via
environment variables:
CLOUDFLARED_TUNNEL_NAME — tunnel name (default: codeman)
CLOUDFLARED_TUNNEL_ID — tunnel UUID (from: cloudflared tunnel list)
CODEMAN_TUNNEL_HOSTNAME — public hostname
Backward compatible: ./tunnel.sh [start|stop|status|url] still works.