Understanding the Bitcoin App web UI

I love my Bitcoin Node, but I’ve been exploring the possibility of creating a DigiByte Node app, using the Bitcoin Node app as a starting point so I can run a second device to support the DigiByte blockchain. I’m confused by the web interface shown above. Where are the files relating to this? I’ve been looking through the Github repo but don’t find any mention of them in the Bitcoin App folder. Are they not part of the app itself? If not, where are they located?