Multiple improvements in authentication functionality

frontend/pubspec.yaml

@@ -35,6 +35,9 @@ dependencies:
   # Use with the CupertinoIcons class for iOS style icons.
   cupertino_icons: ^1.0.8
 
+  # For user credentials and sensitive data
+  flutter_secure_storage: ^9.2.4
+
 dev_dependencies:
   flutter_test:
     sdk: flutter