Wire theme restore/backup into bin/restore.sh and bin/backup.sh

- restore.sh: after folder+venv+frontend restore, runs
  assets/themes/install-theme.sh to rebuild the desktop wiring
- backup.sh: snapshots live xfconf + GTK 3/4 settings.ini into
  assets/themes/restore-snapshot/ before the router mirror, so the
  backup captures actual state (install-theme.sh stays the applier)

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

bin/restore.sh

@@ -36,5 +36,16 @@ echo ""
 echo "Rebuilding frontend dependencies..."
 cd "$NEXUS_ROOT/interface/web" && npm install
 
+echo ""
+echo "Restoring NexusOS desktop theme..."
+theme_installer="$NEXUS_ROOT/assets/themes/install-theme.sh"
+if [ -x "$theme_installer" ]; then
+    "$theme_installer"
+elif [ -f "$theme_installer" ]; then
+    bash "$theme_installer"
+else
+    echo "Warning: $theme_installer not found — skipping theme restore."
+fi
+
 echo ""
 echo "Restore complete. Nexus is ready to start."