Added: login/logout logic, session storage

lib/services/session_manager.dart

@@ -0,0 +1,58 @@
+import 'package:flutter/material.dart';
+import 'package:shared_preferences/shared_preferences.dart';
+
+class SessionManager extends ChangeNotifier {
+  static final SessionManager _instance = SessionManager._internal();
+  factory SessionManager() => _instance;
+  SessionManager._internal();
+
+  bool _loggedIn = false;
+  String? _token;
+  String? _email;
+  String? _name;
+
+  bool get isLoggedIn => _loggedIn;
+  String? get token => _token;
+  String? get email => _email;
+  String? get name => _name;
+
+  final _prefs = SharedPreferencesAsync(); // ✅ New API
+
+  Future<void> init() async {
+    _token = await _prefs.getString('token');
+    _email = await _prefs.getString('email');
+    _name = await _prefs.getString('name');
+
+    _loggedIn = _token != null;
+    notifyListeners();
+  }
+
+  Future<void> login({
+    required String token,
+    required String email,
+    String? name,
+  }) async {
+    await _prefs.setString('token', token);
+    await _prefs.setString('email', email);
+    if (name != null) await _prefs.setString('name', name);
+
+    _token = token;
+    _email = email;
+    _name = name;
+    _loggedIn = true;
+    notifyListeners();
+  }
+
+  Future<void> logout() async {
+    await _prefs.remove('token');
+    await _prefs.remove('email');
+    await _prefs.remove('name');
+
+    _token = null;
+    _email = null;
+    _name = null;
+    _loggedIn = false;
+    notifyListeners();
+  }
+}
+