Add shared multiplayer gear puzzle (Chamber of Motion)

Players open a no-login link and see live cursors and dragged gear
pieces synced in real time, backed by a small Workerman WebSocket
relay (src/Command/PuzzleRelayCommand.php) run alongside symfony
serve - no Docker/Mercure hub needed. The board renders the wall
artwork with a spare-gears tray, and a "Reset puzzle" button (visible
only to logged-in users, verified server-side via a signed token) lets
the DM wipe the shared state for everyone.

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

src/Controller/PuzzleController.php

@@ -0,0 +1,38 @@
+<?php
+
+declare(strict_types=1);
+
+namespace App\Controller;
+
+use App\Puzzle\PuzzleResetTokenSigner;
+use Symfony\Bundle\FrameworkBundle\Controller\AbstractController;
+use Symfony\Component\DependencyInjection\Attribute\Autowire;
+use Symfony\Component\HttpFoundation\Response;
+use Symfony\Component\Routing\Attribute\Route;
+
+/**
+ * Shared, no-login puzzle screens: everyone with the link sees the same
+ * board, the same pieces, and each other's cursors, synced over the
+ * WebSocket relay in {@see \App\Command\PuzzleRelayCommand}.
+ */
+final class PuzzleController extends AbstractController
+{
+    public function __construct(
+        #[Autowire(env: 'PUZZLE_RELAY_PUBLIC_URL')]
+        private readonly string $relayPublicUrl,
+        private readonly PuzzleResetTokenSigner $resetTokenSigner,
+    ) {
+    }
+
+    #[Route('/puzzle/{room}', name: 'app_puzzle_room', requirements: ['room' => '[a-z0-9-]+'], methods: ['GET'])]
+    public function room(string $room): Response
+    {
+        return $this->render('puzzle/room.html.twig', [
+            'room' => $room,
+            'relayPublicUrl' => $this->relayPublicUrl,
+            // Only a logged-in user gets a token that lets them reset the shared
+            // board; anonymous players can play but not wipe it for everyone.
+            'resetToken' => $this->getUser() ? $this->resetTokenSigner->sign($room) : null,
+        ]);
+    }
+}