ObsListItem media finishing

[kueda]

Right now we're using the same ObsImagePreview component for both ObsListItem and ObsGridItem, but they are slightly different. ObsListItem should follow the Photo-List component in the designs:

The goal here is to get the ObsListItem media to match those designs, so here's a probably incomplete list of todos:

• [x] w/ sound + w/o photos should have a centered sound icon, a border, and no background
• [ ] w/o sound + w/o photos should have a centered nophotos icon, a border, and no background
• [x] w/sound + w/ photo should have sound icon in the lower left
• [x] make sure bordered versions are exactly the same width/height as the unbordered ones

[kueda]

Note that Abhas requested that w/o sound + w/o photos continue to use the iconic taxon icon, so that's what I'm going with.

[kueda]

Slowed down a bit by refactoring UI Library so I could preview the different states I was altering, as well as by some back and forth regarding designs that aren't in Figma.