feat(teacher-bff): 完整实现 teacher-bff GraphQL 聚合层

包含 clients/graphql/middleware、health probes、shared-ts contracts 等

services/teacher-bff/src/app.module.ts

@@ -1,8 +1,10 @@
+// 根模块（B1 裁决：P2 起 GraphQL Yoga）
 import { Module } from "@nestjs/common";
-import { TeacherModule } from "./teacher/teacher.module.js";
+import { GraphQLModule } from "./graphql/graphql.module.js";
 import { HealthModule } from "./shared/health/health.module.js";
+import { MiddlewareModule } from "./middleware/middleware.module.js";
 
 @Module({
-  imports: [TeacherModule, HealthModule],
+  imports: [GraphQLModule, HealthModule, MiddlewareModule],
 })
 export class AppModule {}