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

CONTRIBUTING.md

@@ -0,0 +1,41 @@
+# Contributing
+
+## 开发环境要求
+
+- Node.js 20+
+- pnpm 9+
+- Go 1.22+
+- Python 3.12+
+- Docker Desktop
+- buf 1.40+ (`go install github.com/bufbuild/buf/cmd/buf@latest`)
+
+## 开发流程
+
+1. 从 main 创建 feature 分支：`git checkout -b feature/xxx`
+2. 开发并确保 CI 通过：`pnpm lint && pnpm test && pnpm build`
+3. 提交 PR 到 main
+4. CI 全绿后合并
+
+## 提交规范
+
+使用 Conventional Commits：
+
+```
+<type>(<scope>): <description>
+
+types: feat, fix, chore, docs, style, refactor, test, perf, ci
+scope: 服务名或包名（如 api-gateway, classes, shared-proto）
+```
+
+示例：
+- `feat(api-gateway): add JWT auth middleware`
+- `fix(classes): resolve N+1 query in list classes`
+- `docs(004): update service dependency graph`
+
+## 文档同步
+
+修改代码后必须：
+1. 运行 `pnpm run arch:scan` 更新 arch.db
+2. 若架构意图变化，更新 `docs/architecture/004_architecture_impact_map.md`
+3. 若服务接口变化，更新对应 `docs/modules/<service>/README.md`
+4. 若发现新经验，更新 `docs/troubleshooting/known-issues.md`