refactor: 命令树移入 internal/cli，去掉 DefaultRun 注入

- cmd/server/cmd → internal/cli，与 internal/api、internal/proxy 平级
- serve() 移入 cli 包作为默认子命令，main.go 退化为纯入口
- 消除 cmd/cmd 冗余层级和 main → cmd 的回调注入

server/internal/cli/serve.go

@@ -0,0 +1,62 @@
+// Package cli 命令行入口。
+package cli
+
+import (
+	"context"
+	"errors"
+	"log"
+	"net/http"
+	"os"
+	"os/signal"
+	"strconv"
+	"syscall"
+	"time"
+
+	"github.com/openteam/server/internal/api"
+	"github.com/openteam/server/internal/app"
+	"github.com/openteam/server/internal/config"
+	"github.com/openteam/server/internal/proxy"
+)
+
+// serve 启动 HTTP 服务（默认子命令）。
+func serve() error {
+	cfg, err := config.Load()
+	if err != nil {
+		return err
+	}
+
+	a, err := app.New(cfg)
+	if err != nil {
+		return err
+	}
+	defer a.Shutdown(context.Background())
+
+	gw := proxy.NewGateway(a.DB, a.Enc, a.Usage, a.Limit, cfg.RateLimit.UserRPS, cfg.Proxy.LogRaw)
+	router := api.NewRouter(a, gw)
+
+	srv := &http.Server{
+		Addr:              ":" + strconv.Itoa(cfg.Port),
+		Handler:           router,
+		ReadHeaderTimeout: 10 * time.Second,
+	}
+
+	go func() {
+		log.Printf("openteam listening on %s (env=%s)", srv.Addr, cfg.Env)
+		if err := srv.ListenAndServe(); err != nil && !errors.Is(err, http.ErrServerClosed) {
+			log.Fatalf("server: %v", err)
+		}
+	}()
+
+	quit := make(chan os.Signal, 1)
+	signal.Notify(quit, syscall.SIGINT, syscall.SIGTERM)
+	<-quit
+
+	log.Println("shutting down...")
+	ctx, cancel := context.WithTimeout(context.Background(), 10*time.Second)
+	defer cancel()
+	if err := srv.Shutdown(ctx); err != nil {
+		log.Printf("server shutdown: %v", err)
+	}
+	a.Usage.Close()
+	return nil
+}