perf: Redis pub/sub, PgBouncer, optimistic UI for high concurrency

- Add Redis 7 for pub/sub (lobby + chat real-time), rate limiting, caching
- Replace SSE DB polling with Redis pub/sub (lobby: instant approval, chat: instant delivery)
- Add PgBouncer (transaction mode, 500 client → 25 pool connections)
- Chat SSE stream via Redis pub/sub instead of 3s polling
- Optimistic UI in ChatPanel (messages appear before server confirms)
- Redis-based rate limiter (works across multiple app replicas)
- Prisma query optimization (select only needed fields)
- Chat message cache in Redis (10s TTL)
- Docker Compose: add redis, pgbouncer services with healthchecks
- Production: resource limits, 2 app replicas behind Traefik
- Update CLAUDE.md, README.md, .env.example, setup.sh

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

docker-compose.prod.yml

@@ -25,6 +25,13 @@ services:
     environment:
       NEXT_PUBLIC_APP_URL: https://${DOMAIN}
       BETTER_AUTH_URL: https://${DOMAIN}
+    deploy:
+      resources:
+        limits:
+          memory: 1G
+        reservations:
+          memory: 512M
+      replicas: 2
     labels:
       - "traefik.enable=true"
       - "traefik.http.routers.app.rule=Host(`${DOMAIN}`)"
@@ -46,5 +53,23 @@ services:
       - "traefik.http.routers.minio-console.service=minio-console"
       - "traefik.http.services.minio-console.loadbalancer.server.port=9001"
 
+  redis:
+    deploy:
+      resources:
+        limits:
+          memory: 256M
+
+  postgres:
+    deploy:
+      resources:
+        limits:
+          memory: 1G
+
+  ai-agent:
+    deploy:
+      resources:
+        limits:
+          memory: 2G
+
 volumes:
   letsencrypt_data: