fix: scope selector UX, ARIA, and code quality improvements

- removeScope preserves graph state when items remain (only resets on empty)
- Extract shared CheckIcon, CloseIcon, Spinner, ScopeListItem components
- Unify three handleSelect* into single handleToggle
- Fix shared mutable Set in reset state (factory function)
- Add MAX_SCOPE_ITEMS UI feedback (disabled button, warning banner)
- Correct ARIA: dialog > tablist + listbox > option structure
- Event listeners only attached when dropdown is open
- isSelected uses Set lookup via useMemo instead of O(n) scan
- Clear user search only on add, not on deselect

src/locales/ru.json

@@ -1330,7 +1330,8 @@
         "noResults": "Ничего не найдено",
         "removeItem": "Удалить {{label}}",
         "clearAll": "Очистить все выбранные",
-        "addScope": "Добавить область"
+        "addScope": "Добавить область",
+        "maxReached": "Максимум {{max}} элементов"
       },
       "loading": "Загрузка графа...",
       "error": "Ошибка загрузки данных сети",