2FA: implement templates

[stsewd]

Allauth provides some templates for 2FA, but they don't look great with the new theme, and some are very simple.

Some examples:

The templates that we need to override are (the html files only):

• https://github.com/pennersr/django-allauth/tree/64.0.0/allauth/templates/mfa/recovery_codes
• https://github.com/pennersr/django-allauth/tree/64.0.0/allauth/templates/mfa/totp
• https://github.com/pennersr/django-allauth/tree/64.0.0/allauth/templates/mfa

The templates under webauthn we can ignore, since we aren't using that feature.

ref https://github.com/readthedocs/readthedocs.org/pull/11524

[agjohnson]

Those don't look horrible, actually. They will need a pass to clean up though.

The base template allauth uses is maybe a little off, maybe this is a byproduct of the allauth upgrade actually.