RH124 Ch 14: Flatpak Remotes and Apps

RHEL 10 desktops at WebAsha get their apps as Flatpaks. The new internal Flatpak repository lives at `file:///opt/webasha-flatpak` (unsigned, test only). Add it system-wide, install the Notes app, and retire the old remote and its app.

Tasks

  1. Add a system-wide Flatpak remote named webasha for file:///opt/webasha-flatpak. The repository is not GPG-signed.
  2. Install the app com.webasha.Notes from the webasha remote, system-wide.
  3. Uninstall the app com.webasha.OldTool and the runtime it leaves unused.
  4. Remove the remote legacy.