Add Validation

The db_routes.py endpoint works, but what happens if someone requests an artist that doesn't exist? Currently it returns an empty array with no explanation. We need proper error handling. Your directory has been provisioned with the Music Analytics API including db_routes.py that implements the albums endpoint without Pydantic validation or 404 handling — you can view it here: music-analytics-api-with-db-routed/db_routes.py.

Your task is to add Pydantic validation and return a 404 when the artist doesn't exist or has no albums.