fix(tray): pre-create stashed popup to eliminate first-open lag

Pre-create the stashed tray popup during initialization to avoid lag
when first opening it, especially noticeable at high DPI scales (225%).
The popup is opened with zero opacity during startup and closed after
200ms, ensuring all components are fully initialized. This eliminates
the frame drops and stuttering that occurred when hovering over or
clicking the application tray button for the first time.

修复系统托盘折叠弹窗首次打开时的卡顿问题。在初始化时预创建弹窗，
通过设置透明度为0在后台完成组件初始化和渲染，避免首次打开时的
帧率下降和卡顿，特别是在高DPI缩放（225%）下的表现。

PMS: BUG-344705

Author: Ivy233

panels/dock/tray/package/tray.qml

@@ -43,6 +43,9 @@ AppletItem {
 
         property alias dropHover: stashContainer.dropHover
         property alias stashItemDragging: stashContainer.stashItemDragging
+        property bool preCreating: false
+
+        opacity: preCreating ? 0 : 1
 
         popupX: DockPanelPositioner.x
         popupY: DockPanelPositioner.y
@@ -79,8 +82,25 @@ AppletItem {
             DockPanelPositioner.bounding = Qt.binding(function () {
                 return Qt.rect(collapsedBtnCenterPoint.x, collapsedBtnCenterPoint.y, stashedPopup.width, stashedPopup.height)
             })
+            // Pre-create popup to avoid first-open lag
+            Qt.callLater(function() {
+                stashedPopup.preCreating = false
+                stashedPopup.open()
+                preCreateCloseTimer.start()
+            })
         }
     }
+
+    Timer {
+        id: preCreateCloseTimer
+        interval: 200
+        repeat: false
+        onTriggered: {
+            stashedPopup.close()
+            stashedPopup.preCreating = false
+        }
+    }
+
     Connections {
         target: DDT.TraySortOrderModel
         function onActionsAlwaysVisibleChanged(val) {