[feature suggestion] add on-the-fly root authentication for user-installed bauh

[noyannus]

This is not a bug, please read anyway.

Updating flatpaks from a user-installed bauh fails because of missing permissions. [X] Show details says Warning: Flatpak system operation Deploy not allowed for user, and although the update is "complete", after a refresh it is still listed as update. This is very good from the security POV.

However, it would be very convenient to have an option (a dialog) to elevate in a user-installed bauh to root privileges when needed. Otherwise one has to install and run bauh as root, or have additionally a root bauh (but to have /home/<user>/.local/bin/bauh as well as /root/.local/bin/bauh is a bit inelegant).