Introduces VISION_OCR_MODEL setting. When set (e.g. llama3.2-vision:11b), receipt images are transcribed by the Ollama vision model before falling back to Tesseract. Also improves Tesseract preprocessing with adaptive binarisation (autocontrast + threshold at 140) for better accuracy on thermal receipts. Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>