This helps a lot to distinguish keyboard from app in HighContrast mode:
I refrained from adding the border to
adwaita-dark since visual separation is good there but am happy to add it there as well if needed.
This also adds a
GtkBox between the window and the drawing area which allows for for gtk-css out of the box and will make adding more widgets (for e.g. text prediction) easier.
Ideally we'd create a EekWindow that derives from LayerSurface and then uses a ui file to reduce hand crafted GTK but I didn't want to do that without checking first and it can as easily be done afterwards.
Marking as draft because I want to test this a couple of days on device.