Refactor codebase resolving warnings and remove self-package imports

lib/model/accountModel.dart

@@ -0,0 +1,17 @@
+import 'package:flutter/cupertino.dart';
+
+class AccountModel extends ChangeNotifier {
+  bool _isLoggedIn = false;
+
+  bool get isLoggedIn => _isLoggedIn;
+
+  void logout() {
+    _isLoggedIn = false;
+    notifyListeners();
+  }
+
+  void login() {
+    _isLoggedIn = true;
+    notifyListeners();
+  }
+}