fix(install): confirm the file-permissions step on app install

For a generic app (no traefik files, not libreportal) fixPermissionsBeforeStart
prints nothing, so the "Updating file permissions before starting" step showed
its header followed by an empty line — looking like it did nothing. Add an
isSuccessful line after the call so the step reports like every other one.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

scripts/app/install/app_install.sh

@@ -152,6 +152,7 @@ installApp()
         echo "---- $menu_number. Updating file permissions before starting."
         echo ""
         fixPermissionsBeforeStart "$app_name"
+        isSuccessful "File permissions updated for $app_name."
 
         ((menu_number++))
         echo ""