Show landscape photos in correct orientation

We only support portrait mode with the app, which is fine. But if you take a landscape photo, and view it later, it shows up scaled in the middle of the portrait screen. I've removed pan-to-zoom, so it's not a very useful default. We should just show it sideways. The controls can still show in portrait. Snapchat does the same, although they also animate the 90 degree "turn" from the preview to the fullscreen view to make this a bit more obvious.

The issue names no files or tests; start by locating the photo viewing and fullscreen rendering path in the React Native app. Done means landscape photos display sideways in the portrait app while the controls remain portrait-oriented.

Written by the indexing model from the issue text.