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

services/api-gateway/main.go

@@ -0,0 +1,47 @@
+package main
+
+import (
+	"context"
+	"log"
+	"net/http"
+	"os"
+	"os/signal"
+	"syscall"
+	"time"
+
+	"github.com/edu-cloud/api-gateway/internal/config"
+	"github.com/edu-cloud/api-gateway/internal/routing"
+)
+
+func main() {
+	cfg := config.Load()
+
+	r := routing.Setup(cfg)
+
+	srv := &http.Server{
+		Addr:         ":" + cfg.Port,
+		Handler:      r,
+		ReadTimeout:  10 * time.Second,
+		WriteTimeout: 30 * time.Second,
+	}
+
+	// 优雅关闭
+	go func() {
+		log.Printf("API Gateway listening on :%s", cfg.Port)
+		if err := srv.ListenAndServe(); err != nil && err != http.ErrServerClosed {
+			log.Fatalf("listen: %s\n", err)
+		}
+	}()
+
+	quit := make(chan os.Signal, 1)
+	signal.Notify(quit, syscall.SIGINT, syscall.SIGTERM)
+	<-quit
+	log.Println("Shutting down API Gateway...")
+
+	ctx, cancel := context.WithTimeout(context.Background(), 5*time.Second)
+	defer cancel()
+	if err := srv.Shutdown(ctx); err != nil {
+		log.Fatal("Server forced to shutdown:", err)
+	}
+	log.Println("API Gateway exited")
+}