Fix settings window lifecycle

app.go

@@ -31,6 +31,7 @@ type App struct {
 	previousAction *walk.Action
 	nextAction     *walk.Action
 	settingsAction *walk.Action
+	settingsDialog *walk.Dialog
 	timerMu        sync.Mutex
 	timer          *time.Timer
 	busy           atomic.Bool
@@ -194,8 +195,6 @@ func (a *App) refresh(automatic bool) {
 			a.setBusy(false)
 			if err != nil {
 				a.notifyError("刷新壁纸失败：" + err.Error())
-			} else {
-				_ = a.notifyIcon.ShowInfo(appName, "壁纸已刷新。")
 			}
 			if automatic {
 				a.scheduleTimer()