- Fixed column names: brands.name_brand, models.name_model, engines.name_engine
- Added fuzzy model matching with ILIKE %%pattern%% for TecDoc-style names
- Removed erroneous double cur.fetchone() that always returned None
- Added retry logic (3 attempts) for QWEN API empty responses
- Added fallback engine-less query when engine description doesn't match DB
- Protected _extract_json against None input