feat(multiplayer): replace polling with server-sent events and redis pub/sub

lib/redis.ts

@@ -0,0 +1,21 @@
+import Redis from "ioredis";
+
+const url = process.env.REDIS_URL!;
+
+// Client global pour publish/get (réutilisé entre les requêtes via le module cache Node.js)
+const globalForRedis = globalThis as unknown as { redis: Redis | undefined };
+
+export const redis =
+  globalForRedis.redis ??
+  new Redis(url, { lazyConnect: false, maxRetriesPerRequest: 3 });
+
+if (process.env.NODE_ENV !== "production") globalForRedis.redis = redis;
+
+// Crée toujours un nouveau client pour subscribe (ioredis interdit de mixer pub et sub)
+export function createSubscriber(): Redis {
+  return new Redis(url, { lazyConnect: false, maxRetriesPerRequest: 3 });
+}
+
+export function roomChannel(code: string): string {
+  return `room:${code}`;
+}