fix(blockchain-service): 添加系统账户转出事件主题订阅

- 消费者添加订阅 wallet.system-withdrawals 主题
- 解决系统账户转出订单一直处于 FROZEN 状态的问题
- 事件现在可以被 blockchain-service 消费并处理链上转账

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

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

backend/services/blockchain-service/src/infrastructure/kafka/withdrawal-event-consumer.service.ts

@@ -11,6 +11,7 @@ import { Kafka, Consumer, logLevel, EachMessagePayload } from 'kafkajs';
 
 export const WITHDRAWAL_TOPICS = {
   WITHDRAWAL_REQUESTED: 'wallet.withdrawals',
+  SYSTEM_WITHDRAWAL_REQUESTED: 'wallet.system-withdrawals',
 } as const;
 
 export interface WithdrawalRequestedPayload {