fix(docker): 为 zookeeper 和 kafka 挂载时区文件

confluentinc 镜像不支持 TZ 环境变量，需要挂载宿主机时区文件：
- /etc/localtime
- /etc/timezone

🤖 Generated with [Claude Code](https://claude.com/claude-code)

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

backend/services/docker-compose.yml

@@ -61,6 +61,9 @@ services:
       TZ: Asia/Shanghai
       ZOOKEEPER_CLIENT_PORT: 2181
       ZOOKEEPER_TICK_TIME: 2000
+    volumes:
+      - /etc/localtime:/etc/localtime:ro
+      - /etc/timezone:/etc/timezone:ro
     healthcheck:
       test: ["CMD", "nc", "-z", "localhost", "2181"]
       interval: 10s
@@ -88,6 +91,9 @@ services:
       KAFKA_INTER_BROKER_LISTENER_NAME: PLAINTEXT
       KAFKA_OFFSETS_TOPIC_REPLICATION_FACTOR: 1
       KAFKA_AUTO_CREATE_TOPICS_ENABLE: "true"
+    volumes:
+      - /etc/localtime:/etc/localtime:ro
+      - /etc/timezone:/etc/timezone:ro
     healthcheck:
       test: ["CMD", "kafka-topics", "--bootstrap-server", "localhost:9092", "--list"]
       interval: 30s