Replace barcode reader with robust ZXing-CPP implementation

Fix spell check bottom exclusion: Add 115mm exclusion to fallback spell check

Implement improved barcode detection: Use OpenCV contrib with PDF XObject extraction

Remove validation text exceptions: Ignore all errors in bottom 115mm

Fix indentation error in spellchecker import block

Fix spellchecker import error: Use pyspellchecker with fallback imports

Complete setup: Add app.py, update requirements.txt and README.md

Add local files to Hugging Face space

initial commit