Add music recommender domain demo

[Lukas616]

For aolabsai/ao_pyth#9.

Summary

• Adds a music-domain recommender demo with a local sample track catalog.
• Encodes genre, tempo, energy, release recency, vocal/instrumental format, and listening context into binary AO-agent inputs.
• Adds arch__MusicRecommender.py plus a Streamlit app that can run with a live AO Agent or a deterministic local fallback when AO packages are not installed.
• Documents how to run the music demo and corrects the existing README command for the YouTube app.

Validation

• python3 -m unittest discover -s tests
• python3 -m py_compile music_domain.py music_recommender.py arch__MusicRecommender.py tests/test_music_domain.py
• git diff --check

If accepted for the bounty, payment can be sent here: https://paypal.me/Lukas61616