feat(router): add NotFoundHandler for invalid routes

Add a default handler for invalid routes that logs the request details and returns a 404 response. This improves error handling and user experience by providing clear feedback for invalid paths.

router.go

@@ -1,8 +1,8 @@
 package main
 
 import (
+	"fmt"
 	"net/http"
-
 	"super-frpc/postLog"
 )
 
@@ -30,4 +30,12 @@ func setupRoutes() {
 	http.HandleFunc("/frpcAct/instanceMgr/modify", ModifyInstanceHandler)
 	http.HandleFunc("/frpcAct/instanceMgr/list", ListInstancesHandler)
 	http.HandleFunc("/frpcAct/proxyMgr/create", CreateProxyHandler)
+
+	http.HandleFunc("/", NotFoundHandler)
+
+}
+
+func NotFoundHandler(w http.ResponseWriter, r *http.Request) {
+	postLog.Error(fmt.Sprintf("Route not found: %s %s", r.Method, r.URL.Path))
+	SendErrorResponse(w, http.StatusNotFound, "Invalid request path")
 }