Draft: feat: implement multi-factor authentication
Relates to issue #23
This MR was created by Duo in Session 1112005
Changes
- Implement TOTP-based multi-factor authentication system
- Add PyOTP library integration for secure token generation
- Create QR code generation for authenticator app setup
- Implement backup codes system with bcrypt hashing
- Add MFA enrollment and verification user flows
- Create admin override and enforcement capabilities
- Implement comprehensive audit logging for MFA events
- Add rate limiting for verification attempts
- Ensure WCAG 2.1 AA accessibility compliance