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/graphql/graphql.module.ts

@@ -0,0 +1,10 @@
+// GraphQL 模块（B1 裁决：P2 起直接 GraphQL Yoga）
+import { Module } from "@nestjs/common";
+import { GraphQLController } from "./graphql.controller.js";
+import { TeacherModule } from "../teacher/teacher.module.js";
+
+@Module({
+  imports: [TeacherModule],
+  controllers: [GraphQLController],
+})
+export class GraphQLModule {}