fix(tuta): retheme calendar and small elements

[bunfluff]

🔧 What does this fix? 🔧

Fixes unthemed elements on the calendar page and small elements such as the "online" message and settings menu backgrounds
This PR

Closes #1785

🗒 Checklist 🗒

• I have read and followed Catppuccin's contributing guidelines.

[uncenter]

Could you also take a look at the sign up / log in process? Seeing a bunch of unthemed red stuff that would be nice to fix. https://app.tuta.com/login?noAutoLogin=true

[bunfluff]

not everything is fixed (light mode is still a w.i.p., calendar broke again, etc) but i think this is a good enough advancement to get some feedback on :-)
these commits mostly focused on fixing the light mode and theming the log in screen (i still have not taken a look at the sign up screen)