Implement the "Enforce 2FA" feature in the login process.

[NicoPennec]

Problem
When an organization requires two-factor authentication, users without 2FA enabled cannot set it up during the login process.

Solution
Add a two-factor authentication setup component and related functionality:

• Redirect to a new "/login/2fa" page to setup 2FA when required by organization configuration.
• Extract the 2FA setup form in a component to reuse it.
• Modified the app init to redirect to the 2FA setup form on 403 errors.