fix: fix example display issues

Fixed multiple display issues in QML examples:
1. Removed backgroundVisible property from ItemDelegate in exhibition
example as it's no longer needed
2. Changed Rectangle components to Item components in qml-inspect
examples to avoid unnecessary visual elements
3. Removed border.color property from settings dialog example to clean
up the appearance

These changes improve the visual consistency and correctness of the
example displays by using more appropriate QML components and removing
deprecated or unnecessary properties.

Log: Fixed visual display issues in QML examples

Influence:
1. Verify that the exhibition example navigation items display correctly
without backgrounds
2. Check that all qml-inspect examples render properly as Item
components
3. Confirm that the settings dialog example appears without blue borders
4. Test navigation functionality in exhibition example remains working
5. Validate that all examples maintain their intended functionality
after component changes

fix: 修复示例显示问题

修复了 QML 示例中的多个显示问题：
1. 从展览示例的 ItemDelegate 中移除 backgroundVisible 属性，该属性不再
需要
2. 将 qml-inspect 示例中的 Rectangle 组件改为 Item 组件，避免不必要的视
觉元素
3. 移除设置对话框示例中的 border.color 属性以清理外观

这些更改通过使用更合适的 QML 组件和移除已弃用或不必要的属性，提高了示例
显示的视觉一致性和正确性。

Log: 修复 QML 示例中的视觉显示问题

Influence:
1. 验证展览示例中的导航项在没有背景的情况下正确显示
2. 检查所有 qml-inspect 示例作为 Item 组件是否正确渲染
3. 确认设置对话框示例显示时没有蓝色边框
4. 测试展览示例中的导航功能仍然正常工作
5. 验证所有示例在组件更改后保持其预期功能

Author: 18202781743

examples/exhibition/main.qml

@@ -98,7 +98,6 @@ ApplicationWindow {
             model: examplesFiles
             delegate: ItemDelegate {
                 text: modelData.substring(0, modelData.indexOf(".qml"))
-                backgroundVisible: false
                 onClicked: navigation.currentIndex = index
                 checked: navigation.currentIndex === index
             }

examples/qml-inspect/Example_1.qml

@@ -5,7 +5,7 @@
 import QtQuick 2.11
 import org.deepin.dtk 1.0
 
-Rectangle {
+Item {
     MouseArea {
         anchors.fill: parent
         acceptedButtons: Qt.LeftButton | Qt.RightButton

examples/qml-inspect/Example_2.qml

@@ -7,7 +7,7 @@ import QtQuick.Window 2.11
 import QtQuick.Layouts 1.11
 import org.deepin.dtk 1.0
 
-Rectangle {
+Item {
     property string iconStr: "data:image/png;base64,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"
 
     RowLayout {

examples/qml-inspect/Example_colorselector.qml

@@ -5,7 +5,7 @@
 import QtQuick 2.11
 import org.deepin.dtk 1.0
 
-Rectangle {
+Item {
     Label {
         id: changePaletteLabel
         anchors.left: parent.left

examples/qml-inspect/Example_settingsdialog.qml

@@ -6,8 +6,7 @@ import QtQuick 2.0
 import org.deepin.dtk 1.0
 import org.deepin.dtk.settings 1.0 as Settings
 
-Rectangle {
-    border.color: "blue"
+Item {
 
     property list<Settings.SettingsGroup> __groups: [
         Settings.SettingsGroup {