fix: enhance authentication logging and improve server IP handling in FFI Client

[itsalfredakku]

This pull request enhances the authentication process in the VPN client by adding detailed logging throughout the authentication flow and improving type safety for FFI operations. The main focus is on making the authentication process more transparent and easier to debug by reporting key events and errors via callback-based logging.

Authentication process improvements:

• Added a callbacks parameter to the authenticate function and its callers, enabling logging of important events and errors during authentication. Log messages now report the authentication type, password hash decoding steps, network operations, server responses, and error situations. [1] [2] [3] [4] [5]

FFI and type safety improvements:

• Changed the initialization of the server_ip_str array in create_session_from_auth to use std::ffi::c_char for improved FFI compatibility and type safety.… FFI client