feat: tạo hook useNotification.tsx để dùng chung toàn hệ thống

frontend/src/App.tsx

@@ -5,6 +5,7 @@ import { TourDetailPage } from './pages/TourDetailPage';
 import { SignupPage } from './pages/SignupPage';
 import { useTourStore } from './store/useTourStore';
 import { ConfirmProvider } from './hooks/useConfirm';
+import { NotificationProvider } from './hooks/useNotification';
 
 function App() {
   const params = new URLSearchParams(window.location.search);
@@ -84,6 +85,7 @@ function App() {
 
   return (
     <ConfirmProvider>
+      <NotificationProvider>
       {(() => {
         if (currentPage === 'tourDetail') {
           return (
@@ -105,6 +107,7 @@ function App() {
 
         return <LandingPage onContinue={() => setCurrentPage('explore')} onGoToSignup={() => setCurrentPage('signup')} onGoToMap={() => setCurrentPage('explore')} onLoginSuccess={handleLoginSuccess} isInitialSetup={false} />;
       })()}
+      </NotificationProvider>
     </ConfirmProvider>
   );
 }