The frontend is instead deployed from https://github.com/senektra/fullstackopen/tree/main/part3/exercises/phonebook
Deployed to https://fso-phonebook.up.railway.app
For info: https://fso-phonebook.up.railway.app/info
For API: https://fso-phonebook.up.railway.app/api/persons
For frontend: https://fso-phonebook-frontend.up.railway.app
In order to serve the frontend on Railway's platform, it is deployed with Caddy. A Caddyfile specifies hosting configuration and a nixpacks.toml is used to download and install the Caddy server.
I realize this is not how the exercises intended for the frontend to be deployed, but seeing as this course for me is primarily self-study, I saw no harm in a little deviation. I'm also happy that I did, as I now know about Caddy (which is written in Go, one of my favorite languages).