Theming refactor

Theming has been broken off into a seperate space, so that it'll be easier to add lua support later.

Unify import style

Move caching to src/cache/; Finalize API parsing fixes

Font and user cache code has been moved to special files, independant from src/config.rs

API parsing changes have been properly tested, and last.fm API JSON is now trace-logged for debugging convenience.

Reliable user info; Font refactor

Hit a few more endpoints to fix missing images, fallback to default album art just in case.

Refactor the font cache into its own file.

Clippy

Cleanup

Custom font support complete

Add custom font support.

Remove redundant HTML escaping helpers.

fix typo in plain theme breaking light mode.

Create plain theme, do some escaping, fix some busted envvars, document themes.

lots of stuff. theming basically done, added some logging, frontend basically done.

pull down user info

config done

fix packages, implement caching

API deserialization structs