Implement Groq API integration with enhanced features
- Replace Gemini API with Groq API (llama-3.1-8b-instant model)
- Added enhanced OCR with Python-tesseract and OpenCV image preprocessing and PDFPlumber
- Supported Input Formats: PDF files (with OCR fallback) and JPG images (direct OCR processing)
- Implement data flattening for Excel export (each item as separate row)
- Add append functionality to existing Excel files