Implement Two-Factor Authentication (2FA)

[Techhackontime999]

Description

Add TOTP-based two-factor authentication for enhanced account security - a critical security feature for a professional networking platform.

Requirements

• 2FA setup page: generate TOTP secret, show QR code for authenticator apps
• Backup codes: generate 10 one-time-use backup codes on setup
• Login flow: after password, prompt for TOTP code or backup code
• "Remember this device" option (30-day cookie)
• 2FA management: enable/disable, regenerate backup codes
• Recovery flow: use backup codes if authenticator is lost
• Admin enforcement: optional require 2FA for all users
• Security audit log for 2FA events

Files to Create/Modify

• linkup/users/models.py - Add otp_secret, �ackup_codes, is_2fa_enabled, wo_factor_device fields
• linkup/users/views.py - Add 2FA setup, verify, manage views
• linkup/users/forms.py - Add 2FA forms (TOTP input, backup code input)
• linkup/templates/users/two_factor_setup.html - QR code + setup page
• linkup/templates/users/two_factor_verify.html - Login verification page
• linkup/static/js/2fa.js - QR code display, auto-submit

Acceptance Criteria

• Users can enable 2FA with QR code setup
• Login requires TOTP code after password
• Backup codes work for login
• 2FA can be disabled (requires current TOTP)
• "Remember device" works for 30 days