Authentication pages refresh

1. Fixed issue where logging in could result in user seeing an "expired token" error that was difficult to navigate around.
2. Improved visual consistency across various auth-related pages.
3. Added some logic that preserves email address between login/register/reset password pages—this way the user experience is slightly more seamless if, say, they accidentally go to registration flow as an existing user (they won't have to type email address twice).

Uploaded a couple videos of the old and new flows on X here: https://x.com/micahlatty/status/2004967767880204716