feat: add profile screen and update routing; enhance login validation and logout functionality

flutter/lib/core/router/app_router.dart

@@ -2,6 +2,7 @@ import 'package:flutter_riverpod/flutter_riverpod.dart';
 import 'package:go_router/go_router.dart';
 import '../../features/recipes/presentation/recipes_screen.dart';
 import '../../features/auth/presentation/login_screen.dart';
+import '../../features/profile/presentation/profile_screen.dart';
 
 final appRouterProvider = Provider<GoRouter>((ref) {
   return GoRouter(
@@ -15,6 +16,10 @@ final appRouterProvider = Provider<GoRouter>((ref) {
         path: '/recipes',
         builder: (context, state) => const RecipesScreen(),
       ),
+      GoRoute(
+        path: '/profile',
+        builder: (context, state) => const ProfileScreen(),
+      ),
     ],
   );
 });