Add receipt image evaluation cookbook app

[jimbobbennett]

Summary

• add the Gradio receipt extraction and AX evaluation example
• include 14 fictional numbered receipt images
• trace raw GitHub image URLs so AX can use image-aware inputs without embedded base64 payloads

Validation

• compiled receipt_app.py
• verified image discovery for 1.png through 14.png

[github-actions]

🤖 Model version check

✓ No outdated model references in this PR. (policy 2026-08-28)