GNOME Shell + AppIndicator extension opens the attached menu on
left-click in addition to firing SNI Activate, so binding the window
toggle to the click handler made both the window and the menu pop on a
single click. The default Wails3 SystemTray.applySmartDefaults made it
worse: AttachWindow alone is enough to install ToggleWindow as the
implicit click handler, so dropping OnClick wasn't sufficient.
Mirror the legacy Fyne client: skip both AttachWindow and OnClick on
Linux and expose the main window through an explicit "Open NetBird"
menu item. Windows and macOS keep the click-to-toggle behaviour where
the OS cleanly separates left and right click.