filter_string is now a class property

- Support serializing class properties instead of just dataclass fields
- filter_string is now a property that's always up-to-date
- Account display names matching the current SidePane filter are shown

src/qml/SidePane/DelegateRoom.qml

@@ -26,7 +26,6 @@ HInteractiveRectangle {
 
     function activate() {
         pageStack.showRoom(model.user_id, model.data.room_id)
-        print(model.user_id, model.data.room_id)
     }