Install as main frontend for mastodon instance

**Is your feature request related to a problem? Please describe.**
The official mastodon UI is not as pretty as Phanpy, and I would like to be able to have it available as the primary frontend for my instance's users (and myself).

**Describe the solution you'd like**
An ability to use Phanpy as the primary frontend for a Mastodon instance, and a button for accessing instance/user settings.

**Describe alternatives you've considered**
Putting up with the official UI

**Additional context**

No files, tests, or entry points are named. Start by mapping how Phanpy could be deployed as the primary frontend for a Mastodon instance and how instance and user settings are currently accessed. Done would require a defined deployment approach and settings access that works for instance users.

Written by the indexing model from the issue text.