test(models): the user column set includes auth_source and external_id (#5036)

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

tests/test_models.py

@@ -4,7 +4,8 @@ from steward.models.users import User, UserRole
 def test_user_model_fields():
     """User model has all required fields."""
     cols = {c.key for c in User.__table__.columns}
-    assert cols == {"id", "username", "email", "password_hash", "role", "created_at", "is_active"}
+    assert cols == {"id", "username", "email", "password_hash", "role", "created_at", "is_active",
+                    "auth_source", "external_id"}
 
 
 def test_user_role_enum():