fix: udpate blur background on window mode changed

[kegechen]

window frame to fullscreen frame update current background

Issue: linuxdeepin/developer-center#8828

[deepin-ci-robot]

deepin pr auto review

关键摘要:

• 在LauncherController::isFullScreenFrame函数中，直接使用硬编码的字符串"FullscreenFrame"可能会导致维护问题，建议使用常量或枚举来代替。
• 在Appearance::updateCurrentWallpaperBlurhash函数中，对LauncherController::instance().visible()和LauncherController::instance().isFullScreenFrame()的检查可能会导致不必要的性能开销，建议在connect事件连接时进行更详细的检查。
• Appearance::updateCurrentWallpaperBlurhash函数中的两个connect调用可能会导致同一个槽函数被多次调用，这可能不是预期的行为，建议检查是否有必要进行这种连接。

是否建议立即修改:
是

[deepin-ci-robot]

[APPROVALNOTIFIER] This PR is NOT APPROVED

This pull-request has been approved by: BLumia, kegechen

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