Styling needs improving on the login screen

[johnbillion]

The login screen and the 2FA code screen need some styling tweaks.

• Correct the font in the "Back to..." and "Lost your password?" links.
• Correct the font in the text input fields.
• Correct the font and styling for the informational message and error messages.
• Increase the background colour contrast (or change the colour) of the submit button.
• Fix the "Authenticate" button styling.

[richardswain]

Almost all of these are currently sorted. The only issue is with the "Resend Code" button.