fix(admin-service): 添加 Kafka 配置解决用户数据同步问题

添加 KAFKA_BROKERS, KAFKA_CLIENT_ID, KAFKA_CONSUMER_GROUP 环境变量，
使 admin-service 能够正确连接 Kafka 并从 identity-service 同步用户数据。

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

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

backend/services/admin-service/docker-compose.yml

@@ -29,6 +29,10 @@ services:
       - REDIS_PORT=6379
       - REDIS_PASSWORD=${REDIS_PASSWORD:-}
       - REDIS_DB=9
+      # Kafka
+      - KAFKA_BROKERS=kafka:29092
+      - KAFKA_CLIENT_ID=admin-service
+      - KAFKA_CONSUMER_GROUP=admin-service-user-sync
       # File Storage
       - UPLOAD_DIR=/app/uploads
       - BASE_URL=${BASE_URL:-https://rwaapi.szaiai.com/api/v1}