feat(tradein): cian_state_parser shared utility + ScrapedLot Cian fields
- Add cian_state_parser.py: regex-based extractor for window._cianConfig push() entries,
supports direct JSON, JSON.parse() escaped form, and optional demjson3 fallback
- Extend ScrapedLot in base.py with 13 Cian-specific fields (living_area_m2,
bedrooms_count, balconies_count, loggias_count, description_minhash,
cadastral_number, building_cadastral_number, phones, is_homeowner, is_pro_seller,
bargain_allowed, sale_type, metro_stations)
- Add tests/test_cian_state_parser.py with 4 unit tests covering all parse strategies
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