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

setup.py

@@ -1,6 +1,6 @@
 """Setup script for songbox API Client Library"""
 
-from setuptools import setup, find_packages
+from setuptools import find_packages, setup
 
 with open("README.md", "r", encoding="utf-8") as fh:
     long_description = fh.read()
@@ -8,10 +8,7 @@ with open("README.md", "r", encoding="utf-8") as fh:
 # with open("songbox/requirements.txt", "r", encoding="utf-8") as fh:
 #     requirements = [line.strip() for line in fh if line.strip() and not line.startswith("#")]
 
-requirements = [
-    "httpx==0.28.1",
-    "boto3==1.38.32"
-]
+requirements = ["httpx==0.28.1", "boto3==1.38.32"]
 
 setup(
     name="songbox",
@@ -59,4 +56,4 @@ setup(
         "Source": "https://git.cubable.date/CustomIcon/songbox",
         "Documentation": "https://git.cubable.date/CustomIcon/songbox/src/branch/master/README.md",
     },
-)
+)