Improves login security by:
- implementing constant-time authentication to reduce timing attacks
- refactoring user lookup into find_user_by_username_or_email() for username or email login
- introducing a fake user to keep password verification time consistent
- adding a finalize_login hook so plugins can control the authentication flow (2FA, rate limiting, etc.)
Also updates user activity JS to:
- better display action details
- properly handle user lists (login/logout with multiple users)
Linty
0f494baa0c