feat: implement Redis-backed Socket.io adapter and user presence service for cross-instance communication

src/app.module.ts

@@ -6,6 +6,7 @@ import { ScheduleModule } from '@nestjs/schedule';
 import { EventEmitterModule } from '@nestjs/event-emitter';
 
 import { configuration } from './config';
+import { RedisModule } from './common/redis/redis.module';
 import { PrismaModule } from './prisma';
 import { AuthModule, JwtAuthGuard, RolesGuard } from './auth';
 import { UsersModule } from './users';
@@ -35,6 +36,9 @@ import { AppService } from './app.service';
       envFilePath: ['.env.local', '.env'],
     }),
 
+    // Redis (global)
+    RedisModule,
+
     // Rate Limiting
     ThrottlerModule.forRoot([
       {