Key Changes:

• Added configure_2fa function that sets up TOTP-based MFA for the user.
• Configures SSH to require AuthenticationMethods publickey,keyboard-interactive. This enforces a "Key + Code" (or Key + Code + Password) requirement, preventing access if only the private key is compromised.
• Generates and displays the QR code directly in the terminal (via qrencode).
• Includes a "safe rollback" verification step: users must verify a successful login in a new terminal before changes are permanently applied.
• Extracted show_connection_options from configure_ssh into a global helper function to support connection instructions in both SSH and 2FA setup stages.
• Updated the final summary report to indicate 2FA status.