Well, it's just a TS project with a very simple Dockerrile, you can just bun install && bun run prod.
The rest of the dependencies aren't included in the docker image.
To be fair, I prefer nodejs/npm to have as little to do with my home folder as possible, and not have to worry about maintaining my own versions/updates/etc. as I am not a regular user of JS, don't already have the toolchain(s) and don't want to.
This is about making your own personal instance of a microblog that's ActivityPub enabled. It's much lighter than running Mastodon that's mean to be a hosting platform for a lot of users.