fix(identity-service): change dynamic import to static import

Dynamic imports with path aliases (@/domain/events) don't work at runtime.
Changed to static import to fix module resolution error.

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

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

backend/services/identity-service/src/application/services/user-application.service.ts

@@ -18,6 +18,7 @@ import { BlockchainClientService } from '@/infrastructure/external/blockchain/bl
 import { MpcWalletService } from '@/infrastructure/external/mpc';
 import { ApplicationError } from '@/shared/exceptions/domain.exception';
 import { generateRandomIdentity } from '@/shared/utils';
+import { MpcKeygenRequestedEvent } from '@/domain/events';
 import {
   AutoCreateAccountCommand, RecoverByMnemonicCommand, RecoverByPhoneCommand,
   AutoLoginCommand, RegisterCommand, LoginCommand, BindPhoneNumberCommand,
@@ -127,7 +128,6 @@ export class UserApplicationService {
     account.clearDomainEvents();
 
     // 10. 发布 MPC Keygen 请求事件 (触发后台生成钱包)
-    const { MpcKeygenRequestedEvent } = await import('@/domain/events');
     const sessionId = crypto.randomUUID();
     await this.eventPublisher.publish(new MpcKeygenRequestedEvent({
       sessionId,