Function setup_ssh 

pub fn setup_ssh() -> Result<(), Box<dyn Error>>

Configures SSH for improved security.

This function modifies the SSH configuration to:

• Disable root login
• Disable password authentication (requiring key-based authentication)
• Change the default SSH port (TODO: implement this securely)

After making changes, it restarts the SSH service to apply the new configuration.

Returns

Returns Ok(()) if SSH is configured successfully, or an error if configuration fails.