Add a way to save what theme you select to your account instead of just using cookies.

[Frerduro]

Please confirm the following.

• I checked the existing issues for duplicate feature requests

What parts of Modrinth is your feature request related too?

Modrinth.com website

Is your suggested feature related to a problem? Please describe.

I am frustrated I constantly have to go to my settings to switch to the theme I want to use. I don't understand why the setting isn't saved to my user account.

Describe the solution you'd like

Save the theme you select to your account.

Describe alternatives you've considered

No response

Additional context

No response