Fix bottom panel focus not showing

[lodetrick]

Fixes #113898

There are no hints for focus on the bottom panel (the focus stylebox is invisible) so it is hard to tell when the bottom panel has focus. This PR adds the focus hint to both themes mirroring the TabContainer's focus hint.

Classic	Modern

[YeldhamDev]

How does this fixes the issue?

[KoBeWi]

I think the idea is to make bottom panel consistent with other docks?
tbh maybe you could do the opposite and remove the focus from side docks. I encountered a similar problem in #113051

[YeldhamDev]

I think showing the focus on keyboard input is fine, but it shouldn't show it by just having it opened by selecting a node/resource.

[lodetrick]

This PR is for consistency, yes. It is just for the theming and not for the actual taking of focus (which I do think should change, but that would be in a separate PR).

The choice is either to show focus on both or neither, I think inconsistency is bad here. I'm partial to both because it gives more information to the user and once force focusing is fixed it should only be done intentionally through keyboard input.