feat: add go backend skeleton

cmd/codex-agent-manager/main.go

@@ -0,0 +1,21 @@
+package main
+
+import (
+	"fmt"
+	"net/http"
+
+	"codex-agent-manager/internal/app"
+)
+
+func main() {
+	cfg := app.DefaultConfig()
+	mux := http.NewServeMux()
+	mux.HandleFunc("/api/health", func(w http.ResponseWriter, r *http.Request) {
+		w.Header().Set("Content-Type", "application/json")
+		_, _ = w.Write([]byte(`{"status":"ok"}`))
+	})
+	fmt.Printf("Codex 智能体管理台监听 http://%s\n", cfg.HTTPAddr)
+	if err := http.ListenAndServe(cfg.HTTPAddr, mux); err != nil {
+		panic(err)
+	}
+}