Modern Style Fallbacks

Changes:
- Formatted occurrences of the `aspect-ratio` property, and it's fallback styles. They are just a little tidier now.

Fixes:
- Wrapped a `:focus-visible` occurrence that was part of a multi-selector line, which prevented the whole style block from being applied when in Safari. Now that Safari supports the forgiving selector list for `:where()`, I just wrapped `:focus-visible` inside of one of those, and that allowed other use cases for the selector to be applied as intended! Very neat, I love `:where()` :P

Removals:
- Removed fallbacks for the `:where()` selector throughout the app's styles. It's supported almost everywhere now, as well as with forgiving selector lists! This is a huge bonus. It makes fixes like the one above possible now :)