fix(mining-admin-service): 用户列表API添加nickname字段

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

backend/services/mining-admin-service/src/application/services/users.service.ts

@@ -434,6 +434,7 @@ export class UsersService {
     return {
       accountSequence: user.accountSequence,
       phone: this.maskPhone(user.phone),
+      nickname: user.nickname || null,
       status: user.status,
       kycStatus: user.kycStatus,
       realName: user.realName,