refactor(clients): reorganize client modules into clients package

- Move auth, user, and music clients into new clients package
- Update imports to use new module paths
- Add __init__.py to expose clients from package
- Clean up code formatting and imports
- Add pre-commit configuration for code quality checks

requirements.txt

@@ -1,2 +1,2 @@
+boto3==1.38.32
 httpx==0.28.1
-boto3==1.38.32