> Add error handling to the /artists endpoint.

Done. I've added error handling to /artists (routes.py:9-19):
- Try-except block wrapping retrieval and serialization
- AttributeError handler if the data store isn't initialized
- General exception handler returning error details with 500 status

return jsonify({'error': f'Failed to retrieve artists: {str(e)}'}), 500

> Don't expose exception details to users, that's a security risk. Log internally 
and return a generic message.  Update CLAUDE.md.

Updated /artists to log errors internally and return a 
generic 500 message. CLAUDE.md updated with the convention: 
never expose exception details in responses.