fix namespace and use spelling mistake

apps/backend/routes/notifications.php

@@ -1,6 +1,6 @@
 <?php
 
-use app\Http\Controllers\NotificationsController;
+use App\Http\Controllers\NotificationsController;
 use Illuminate\Support\Facades\Route;
 
 Route::middleware(['web', 'auth:sanctum'])->get('/users/notifications', [NotificationsController::class, "getNotifications"]);