[Admin UI] Build + serve admin UI

[seanpreston]

Is your feature request related to a specific problem?

We'll need to add some commands to the Dockerfile and some dev commands to the Makefile to build and serve the frontend.

Describe the solution you'd like

A description of what you want to happen.

Describe alternatives you've considered, if any

A description of any alternative solutions or features you've considered.

Additional context

Add any other context or screenshots about the feature request here.

[TheAndrewJackson]

@seanpreston Do you have some example commands or env vars that you're expecting the Makefile and Dockerfile to have and use?

Currently, my implementation always builds and serves the UI.