Implement Two-Factor Authentication (2FA)

[ValeriaMaltseva]

Currently, the frontend only provides a toggle in the settings to enable/disable 2FA. However, enabling 2FA does not affect the login flow yet.

The required backend functionality should already be available, so this task is focused on implementing the missing frontend logic and integrating the 2FA flow into the authentication process.

[idaiv]

https://www.figma.com/design/pg65AmcoU5iVtQeroHK4iF/Full-Screens?node-id=11572-168169&t=7NREFCcDWiYQGpEw-4