Allow room members to view room photo full size

It is possible to tap member avatars to open a member info page, from which you can tap their profile photo and view it full size. It is not possible to see the room photo full size, however. The Android and Electron-based apps allow full-size room photo viewing, so it would be nice to have this ability on the iOS app.

Start by tracing the iOS room-photo interaction and compare it with the existing member-avatar full-size viewing flow; the issue also points to the Android and Electron apps as behavior references. Done means an iOS user can open the room photo at full size from the room interface.

Written by the indexing model from the issue text.