fix: Gate E2E — Test.createTestingModule + DiscoveryModule

DiscoveryModule 来自 @nestjs/core，提供 ModulesContainer 和 Reflector。
解决了 AdminAuthGuard 和 DiscoveryService 的依赖解析问题。

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

test/m-ai-03-gate.e2e-spec.ts

@@ -1,5 +1,6 @@
-import { NestFactory } from '@nestjs/core';
+import { Test, TestingModule } from '@nestjs/testing';
 import { INestApplication } from '@nestjs/common';
+import { DiscoveryModule } from '@nestjs/core';
 import { JwtService } from '@nestjs/jwt';
 import request from 'supertest';
 import { AppModule } from '../src/app.module';
@@ -40,15 +41,18 @@ describe('M-AI-03 GATE E2E (fail-closed)', () => {
     process.env.AI_JOB_SYNTHETIC_ENABLED = 'true';
     process.env.JWT_SECRET = 'gate-e2e-secret';
 
-    // NestFactory.create 提供所有 core providers (Reflector etc.)
-    // 连接 Prisma + Redis — 失败则测试 fail-closed
-    app = await NestFactory.create(AppModule);
+    // DiscoveryModule 提供 ModulesContainer + Reflector（TestingModule 不自动导入）
+    const module: TestingModule = await Test.createTestingModule({
+      imports: [AppModule, DiscoveryModule],
+    }).compile();
+
+    app = module.createNestApplication();
     await app.init();
 
-    creationService = app.get(AiJobCreationService);
-    registry = app.get(JobDefinitionRegistry);
-    lifecycleRepo = app.get(AiJobLifecycleRepository);
-    jwtService = app.get(JwtService);
+    creationService = module.get(AiJobCreationService);
+    registry = module.get(JobDefinitionRegistry);
+    lifecycleRepo = module.get(AiJobLifecycleRepository);
+    jwtService = module.get(JwtService);
 
     userToken = jwtService.sign({ sub: TEST_USER, email: 'gate@test.com', role: 'USER', type: 'user' });
   }, 30000);