applets/kickoff: block hovering until mouse moves

Kickoff already has an implementation of hover blocking for searching: once the user starts typing, it will not automatically select and focus the item under the mouse, so keyboard navigation behaves consistently no matter where the mouse is (unless the user accidentally moves it). The same is not true for when the applet initially opens; then the selected item changes depending on the mouse position, and users cannot build muscle memory to launch favorites - e.g. opening Kickoff with a keyboard shortcut and immediately pressing Return will not always launch the same favorite.

We can just move the existing hover block, which is specific to the search results, directly into the FullRepresentation, and adjust things slightly to set the correct internal state depending on the context. This makes hover blocking work for all of (expanded) Kickoff.