fix: center dialog title with vertical offset

1. Replace plain title text with a centered D.Label in DialogTitleBar
2. Align title horizontally centered and vertically offset downward by 30px
3. Constrain title max width to prevent overlapping with side buttons

Log: Center the dialog window title with downward offset and width limit

fix: 对话框标题居中并添加垂直偏移

1. 将 DialogTitleBar 中的纯文本标题替换为居中的 D.Label 组件
2. 标题水平居中，垂直方向向下偏移 30 像素
3. 限制标题最大宽度，避免与两侧按钮重叠

Log: 将对话框窗口标题居中并设置下移偏移和宽度限制
PMS: BUG-361279

Author: MyLeeJiEun

qt6/src/qml/DialogWindow.qml

@@ -62,7 +62,25 @@ Window {
                 sourceComponent: DialogTitleBar {
                     enableInWindowBlendBlur: false
                     icon.name: control.icon
-                    title: control.title
+                    D.Label {
+                        text: control.title
+
+                        // --- 水平居中 ---
+                        anchors.horizontalCenter: parent.horizontalCenter 
+
+                        // --- 垂直居中并向下偏移 ---
+                        anchors.verticalCenter: parent.verticalCenter
+                        anchors.verticalCenterOffset: 30 // 正数向下移，根据视觉效果调整
+
+                        // --- 样式设置 ---
+                        font: titleBar.font 
+                        palette: titleBar.palette
+
+                        // 限制最大宽度，避免文字太长冲到左右两边的按钮或图标
+                        width: Math.min(implicitWidth, parent.width - 120)
+                        elide: Text.ElideRight
+                        horizontalAlignment: Text.AlignHCenter
+                    }
                 }
             }