Show marketing opt-in status in admin users overview

Adds a Marketing column to the admin users table and a total opt-in
count in the header, so admins can see who signed up for updates on
future projects.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

src/Game/Controller/GameAdminUserController.php

@@ -22,8 +22,11 @@ final class GameAdminUserController extends AbstractController
     #[Route('', name: 'game_admin_users', methods: ['GET'])]
     public function index(UserRepository $userRepository): Response
     {
+        $users = $userRepository->findBy([], ['id' => 'ASC']);
+
         return $this->render('game/admin/users/index.html.twig', [
-            'users' => $userRepository->findBy([], ['id' => 'ASC']),
+            'users' => $users,
+            'marketingOptInCount' => count(array_filter($users, static fn (User $user) => $user->isMarketingOptIn())),
         ]);
     }