packaging: ship authforge-gnome-integration binary package

Declares the new arch-all binary package in debian/control (depending on
authforge-gui + gnome-control-center) and wires its single data file
(gnome-integration/io.dangerousthings.AuthForge.UsersPanel.desktop) into
debian/rules' override_dh_auto_install so it lands in
/usr/share/applications/. The metapackage already Suggests:
authforge-gnome-integration, so no change there.

debian/control

@@ -53,3 +53,11 @@ Architecture: any
 Depends: ${shlibs:Depends}, ${misc:Depends}, authforge-daemon
 Description: GTK4/libadwaita UI for authforge
  End-user-facing settings panel for enrollment and policy.
+
+Package: authforge-gnome-integration
+Architecture: all
+Depends: ${misc:Depends}, authforge-gui, gnome-control-center
+Description: GNOME Settings Users-panel integration for authforge
+ Adds a "Configure security…" entry to each user's detail view in
+ gnome-control-center, launching the AuthForge GUI with that user
+ pre-selected.