fix(settings): leave user manage view when switching admin sections (#1649)

The admin panel stays mounted across Settings pages, so an open user
manage view kept replacing every other admin section until Back to users
was clicked. Reset it whenever the selected section changes.

src/ui/sidebar/AdminSettingsPanel.tsx

@@ -217,6 +217,12 @@ export function AdminSettingsPanel({
     setUserPage(0);
   }, [userSearch]);
 
+  // The panel stays mounted across Settings pages, so an open user view
+  // would otherwise replace whichever section is picked next.
+  useEffect(() => {
+    setManageUser(null);
+  }, [section]);
+
   useEffect(() => {
     onEditingChange?.(manageUser !== null);
     return () => onEditingChange?.(false);