Replace manual signal handling in runDaemon() with kardianos/service
for cross-platform service lifecycle (Start/Stop/Run). Add daemon
start/stop/restart subcommands using service.Control(), and improve
status detection with s.Status() plus socket-check fallback.
Custom macOS install logic (dscl, sudoers, pf, plist generation)
is unchanged — only the runtime lifecycle is delegated to the library.
