feat(realtime): Socket.IO Redis adapter — enable horizontal scaling

- RedisIoAdapter wires @socket.io/redis-adapter with dedicated pub/sub clients
- channel key 'tripz:sio' isolates on shared Redis
- wired in main.ts via useWebSocketAdapter; multiple app replicas can now share WS connections

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

backend/src/main.ts

@@ -4,11 +4,17 @@ import { ValidationPipe, Logger } from '@nestjs/common';
 import { ConfigService } from '@nestjs/config';
 import { DocumentBuilder, SwaggerModule } from '@nestjs/swagger';
 import { AppModule } from './app.module';
+import { RedisIoAdapter } from './realtime/redis-io.adapter';
 
 async function bootstrap() {
   const app = await NestFactory.create(AppModule);
   const cfg = app.get(ConfigService);
 
+  // مُحوّل Socket.IO عبر Redis — يفعّل التوسّع الأفقي (عدة نسخ)
+  const redisIoAdapter = new RedisIoAdapter(app, cfg);
+  await redisIoAdapter.connectToRedis();
+  app.useWebSocketAdapter(redisIoAdapter);
+
   app.setGlobalPrefix('api');
   app.useGlobalPipes(
     new ValidationPipe({ whitelist: true, transform: true }),