There was no .dockerignore, so node_modules and build/ were copied into the
build context on every build. Add one, install from the lockfile with npm ci,
prune the dev dependencies out of the runtime layer and run as the node user.
Updates the compose build context, the Dockerfile header, the package
name and the docs. The compose service and container keep the name
frontend/musify-frontend, since nginx routes to http://frontend:3000.
The source files also carry the first prettier pass, so the rename and
the reformat land together for them.
Admin