feat(p1): complete P1 foundation stage

- monorepo: pnpm workspace + go.work + pyproject.toml + commitlint/husky
- infra: docker-compose (minimal + full profiles) + init-sql + prometheus
- arch-scan: multi-language scanner skeleton (TS/Go/Python/Proto)
- shared-proto: buf v2 + classes.proto (ClassService CRUD contract)
- api-gateway: Go/Gin + JWT HS256 auth + reverse proxy + request ID
- classes: NestJS golden template (error system + observability + middleware + CRUD + tests)
- teacher-portal: Next.js + paper-feel UI design system
- CI/CD: 4 workflows (go/ts/py/proto)
- docs: migration guide + project_rules + coding-standards + git-workflow + ui-design-system + 004 + 9 module READMEs + known-issues + spec/plan migration + roadmap

packages/shared-proto/proto/classes.proto

@@ -0,0 +1,58 @@
+syntax = "proto3";
+
+package next_edu_cloud.classes.v1;
+
+// ClassService 定义班级域 CRUD 契约
+// P1: REST 实现，P3 起转 gRPC
+service ClassService {
+  rpc CreateClass(CreateClassRequest) returns (Class);
+  rpc GetClass(GetClassRequest) returns (Class);
+  rpc ListClasses(ListClassesRequest) returns (ListClassesResponse);
+  rpc UpdateClass(UpdateClassRequest) returns (Class);
+  rpc DeleteClass(DeleteClassRequest) returns (Empty);
+}
+
+message Class {
+  string id = 1;
+  string name = 2;
+  string grade_id = 3;
+  string head_teacher_id = 4;
+  string description = 5;
+  int64 created_at = 6;
+  int64 updated_at = 7;
+}
+
+message CreateClassRequest {
+  string name = 1;
+  string grade_id = 2;
+  string head_teacher_id = 3;
+  string description = 4;
+}
+
+message GetClassRequest {
+  string id = 1;
+}
+
+message ListClassesRequest {
+  string grade_id = 1;
+  int32 page_size = 2;
+  string page_token = 3;
+}
+
+message ListClassesResponse {
+  repeated Class classes = 1;
+  string next_page_token = 2;
+}
+
+message UpdateClassRequest {
+  string id = 1;
+  optional string name = 2;
+  optional string head_teacher_id = 3;
+  optional string description = 4;
+}
+
+message DeleteClassRequest {
+  string id = 1;
+}
+
+message Empty {}