Gather the CLI command modules into a commands sub-package

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

tools/tests/test_fetch_artists.py

@@ -16,7 +16,8 @@ from unittest import mock
 
 from sqlalchemy.orm import Session
 
-from pop_fem_audit_tools import config, fetch_artists
+from pop_fem_audit_tools import config
+from pop_fem_audit_tools.commands import fetch_artists
 from pop_fem_audit_tools.database import Base, DataSource
 from pop_fem_audit_tools.models import Artist, Role, Song, SongArtist