fix: remove KWin blur from DialogWindow to fix dark theme issue

1. Remove enableBlurWindow: true default from DialogWindow.qml
2. Set color to transparent directly instead of conditional on enableBlurWindow

Influence:
1. All DialogWindow instances will no longer use KWin blur
2. Dialog windows will use standard DTK palette without blur side effects
3. Applications forcing dark theme will not affect dialog appearance

fix: 从 DialogWindow 移除 KWin blur 以修复深色主题问题

1. 从 DialogWindow.qml 中移除 enableBlurWindow: true 默认值
2. 将 color 直接设为 transparent，不再依赖 enableBlurWindow 条件判断

Influence:
1. 测试所有使用 DialogWindow 的对话框在浅色/深色主题下的显示
2. 验证 dde-launchpad 卸载确认对话框在浅色系统主题下不再显示深色
3. 检查其他 DTK 应用（如关于对话框）的 blur 效果是否正常
4. 在不同屏幕分辨率和缩放比例下进行测试

PMS: BUG-359629

Author: robertkill

qt6/src/qml/DialogWindow.qml

@@ -19,10 +19,9 @@ Window {
     D.DWindow.enableSystemResize: false
     D.DWindow.motifFunctions: D.WindowManagerHelper.FUNC_ALL & ~D.WindowManagerHelper.FUNC_RESIZE
     D.DWindow.wmWindowTypes: D.WindowManagerHelper.DialogType
-    D.DWindow.enableBlurWindow: true
     flags: Qt.Dialog | Qt.WindowCloseButtonHint | Qt.MSWindowsFixedSizeDialogHint
     D.ColorSelector.family: D.Palette.CrystalColor
-    color: D.DWindow.enableBlurWindow ? "transparent" : (active ? D.DTK.palette.window : D.DTK.inactivePalette.window)
+    color: "transparent"
     height: content.height
     width: content.width