R1:1f51d023af12

Improve Pholio on mobile

Summary:
Ref T2644. This isn't perfect, but makes Pholio more-or-less usable on mobile. In particular:

- Inline comments drop below the image.
- Clicking the image lightboxes a full size version so you can scroll around it and inspect details.
- Clicking it again dismisses it.

Things that aren't good:

- Can't add inline comments. This seems complicated and not critical.
- Can't easily figure out which inline comments go where since there's no hover. Maybe let you tap…