refactor(reward): remove unused transferExpiredRewardToOperationAccount method

Expired referral rewards are transferred to headquarters community (seq=1),
not operation account. Remove the unused method to avoid confusion.

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

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

backend/services/reward-service/src/infrastructure/external/authorization-service/authorization-service.client.ts

@@ -67,38 +67,4 @@ export class AuthorizationServiceClient implements IAuthorizationServiceClient {
       return null;
     }
   }
-
-  /**
-   * 通知过期奖励转入运营账户
-   * 根据文档：过期的直推奖励应转入运营账户
-   */
-  async transferExpiredRewardToOperationAccount(params: {
-    amount: number;
-    sourceRewardId: bigint;
-    memo?: string;
-  }): Promise<void> {
-    try {
-      const response = await fetch(
-        `${this.baseUrl}/api/v1/system-accounts/receive-expired-reward`,
-        {
-          method: 'POST',
-          headers: {
-            'Content-Type': 'application/json',
-          },
-          body: JSON.stringify({
-            accountType: 'OPERATION_ACCOUNT',
-            amount: params.amount,
-            sourceRewardId: params.sourceRewardId.toString(),
-            memo: params.memo || '过期奖励转入',
-          }),
-        },
-      );
-
-      if (!response.ok) {
-        this.logger.warn(`Failed to transfer expired reward to operation account`);
-      }
-    } catch (error) {
-      this.logger.error(`Error transferring expired reward:`, error);
-    }
-  }
 }