applets/clipboard: Remove invalid Layout properties and fix horizontal scrolling

applets/clipboard: Remove invalid Layout properties and fix horizontal scrolling

ClipboardPage does not have a layout attached, so remove its Layout.* properties.

contentWidth is explicitly set to 0 to avoid horizontal scrolling.

applets/clipboard: Fix activeFocus not being switched to item

The list item will regain focus after clicking buttons in the heading and clicking the list item now.