It's at a very simple stage for now:
- Tab control is no longer recreated when friends change, counts are
updated as bindables.
- All async logic removed temporarily.
- Sort and filtering happens in realtime without panel reload.
- Display modes removed for now. Need to think about this one a bit more,
and whether to retry the async path or look for a separate solution.
- Real time user presence is now considered. Not considered for sorting
by last visit time yet.
It's all a bit weird so let's just disable it for now. For instance,
this is exposed as "text" font / colour but only affects the header.
Also, no other headers are cusotmisable in similar components.