IPP 4.0 lets visitors upload through a second, optional app in the same
repository. The addon now builds the whole workspace, so upload-app is
always ready, and can run it as immich-proxy-upload on port 3001: asked
on install (var_ipp_uploads), offered in the menu of an existing
install, rebuilt and restarted on update with its config.json kept, and
removed on uninstall. It stays off unless chosen.