Dark mode visual bugs

[zackkrida]

Description

This is a meta issue to track all dark mode bugs identified in the testing #4783.

• [ ] #4829
• Textarea text is incorrect color
• Some focus rings are missing/incorrect/using the browser default:
  • [ ] #4958
  • Source in audio details page
  • Footer items
  • Header items
  • Clear button in search input in Search header
  • ...and more, potentially
• [x] #4910
• Some focus rings have a white halo in dark mode:
  • [ ] #4959 components using focus-bold-filled style: image and audio on All content results
  • [ ] #4958 Links in body content in all internal pages, Link in filter safe browsing section
  • Links in Attribution box
  • [x] #4939 VSelectField (theme switcher, language switcher)
  • ...and more, potentially
• In light and dark mode: The search input changes the background color when it should just change the placeholder color.
• Audio playhead is incorrect color
• Report button disabled state is incorrect

[obulat]

While trying to fix the "white halo" around the focus outlines, I found this article about outline-style: auto: it's not a bug, but a feature in Chrome.

Of course, since we do change the colors of outlines based on the background color, we can override it using outline-style: solid or outline-style:none (when using the box-shadow from Tailwind ring).