Use noise protocol on handshake. Check peer's public key if needed. Also support rekey and replay attack prevention.
E2EE and temporary password will be implemented based on this.
This PR fundamentally restructures the EasyTier GUI, introducing support for service mode and remote mode, transforming it from a simple desktop application into a powerful network management terminal. This change allows users to persistently run the EasyTier core as a background service or remotely manage multiple EasyTier instances, greatly improving deployment flexibility and manageability.