refactor: Simplify platform-specific icon handling in AppCustomizationPage and ProfilePage

- Replaced direct platform checks with a utility method `UiUtils.platformIcon` for better readability and maintainability.
- Updated localization strings for app customization to enhance clarity and consistency across multiple languages.
- Adjusted icon colors in the UI to ensure proper theming and visual consistency.

lib/l10n/app_localizations_fr.dart

@@ -697,7 +697,7 @@ class AppLocalizationsFr extends AppLocalizations {
   String get failedToDeleteFolder => 'Échec de la suppression du dossier';
 
   @override
-  String get aboutApp => 'À propos de l’application';
+  String get aboutApp => 'À propos';
 
   @override
   String get aboutAppSubtitle => 'Informations et liens Conduit';
@@ -883,11 +883,10 @@ class AppLocalizationsFr extends AppLocalizations {
   }
 
   @override
-  String get appCustomization => 'Personnalisation de l\'app';
+  String get appCustomization => 'Personnalisation';
 
   @override
-  String get appCustomizationSubtitle =>
-      'Personnalisez l\'affichage des noms et de l\'UI';
+  String get appCustomizationSubtitle => 'Thème, langue, voix et quickpills';
 
   @override
   String get quickActionsDescription =>