index-modern.html refers to styling/, javascript/ and images/ as if they sat
next to it, but they live under frontend/. Only docker/entrypoint.sh reconciles
that, by flattening those directories into the web root, so serving the
repository as it stands renders the page without stylesheet, script or logo.
Point the HTML at frontend/, have the entrypoint copy that directory as-is, and
move settings.json and server-list.json to the root that the page fetches them
from, so the repository layout and the deployed layout are the same. Update the
install instructions, which described the flattening.
