fix(infra): 添加 Zookeeper 数据持久化卷，修复 Kafka Cluster ID 冲突

Kafka 有持久化卷但 Zookeeper 没有，导致 down/up 后 ZK 生成新的
Cluster ID，与 Kafka meta.properties 中的旧 ID 冲突。

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

backend/services/docker-compose.yml

@@ -76,6 +76,8 @@ services:
       # Java timezone for confluentinc images
       KAFKA_OPTS: "-Duser.timezone=Asia/Shanghai"
     volumes:
+      - zookeeper_data:/var/lib/zookeeper/data
+      - zookeeper_log:/var/lib/zookeeper/log
       - /etc/localtime:/etc/localtime:ro
       - /etc/timezone:/etc/timezone:ro
       - /usr/share/zoneinfo:/usr/share/zoneinfo:ro
@@ -777,6 +779,10 @@ volumes:
     driver: local
   admin_uploads_data:
     driver: local
+  zookeeper_data:
+    driver: local
+  zookeeper_log:
+    driver: local
   kafka_data:
     driver: local