Allow to set theme + color scheme without a user

[oskarrough]

Would be cool if users can set their prefered theme and colorScheme without being signed in.

Currently blocks access if you aren't signed in.

https://github.com/radio4000/components/blob/main/src/components/r4-user-account.js

How could we do this?

• Refactor to always read/write theme+colorScheme into localstorage first
• The account should reflect what's in localstorage