fix: 修复 macOS 桌面应用打包与元数据

将 macOS 桌面应用改为通用二进制并动态写入最低系统版本，避免 Intel Mac 无法启动。统一桌面应用名称与托盘展示，并补充测试确保相关行为稳定。

backend/cmd/desktop/port_test.go

@@ -1,6 +1,7 @@
 package main
 
 import (
+	"errors"
 	"net"
 	"net/http"
 	"testing"
@@ -21,19 +22,12 @@ func TestCheckPortAvailable(t *testing.T) {
 func TestCheckPortOccupied(t *testing.T) {
 	port := 19827
 
-	listener, err := net.Listen("tcp", "127.0.0.1:19827")
+	listener, err := net.Listen("tcp", ":19827")
 	if err != nil {
 		t.Fatalf("无法启动测试服务器: %v", err)
 	}
 	defer listener.Close()
 
-	go func() {
-		conn, err := listener.Accept()
-		if err == nil {
-			conn.Close()
-		}
-	}()
-
 	time.Sleep(100 * time.Millisecond)
 
 	err = checkPortAvailable(port)
@@ -56,7 +50,7 @@ func TestCheckPortAvailableAfterClose(t *testing.T) {
 	defer server.Close()
 	go func() {
 		err := server.Serve(listener)
-		if err != nil && err != http.ErrServerClosed {
+		if err != nil && err != http.ErrServerClosed && !errors.Is(err, net.ErrClosed) {
 			t.Errorf("serve failed: %v", err)
 		}
 	}()