Areas page now shows a single TreeView with sites as roots and areas as
children. Context menus: sites get "Add Area", areas get "Add Child Area",
"Edit Area", "Delete Area" — each navigating to a dedicated page.
The Delete Area page shows a TreeView of the area and all recursive children
with assigned instances. Deletion is blocked if any instances are assigned
to the area or its descendants.
Joseph Doherty
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