Add _extract_obj_class_from_ai() with regex patterns for Комфорт/Бизнес/Премиум/Элит/Стандарт.
_norm_object() uses it as fallback; objClass from API still takes priority if ever returned.
Add backfill SQL 105 to retroactively populate existing rows from raw JSON payloads.
Coverage: ~1806/4548 rows will be filled; remainder NULL is expected (Нежилое/no AI desc).
