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

examples/download_songs.py

@@ -0,0 +1,14 @@
+from songbox import SongboxClient
+
+client = SongboxClient()
+verify_id = client.auth.login("960", "777777")
+otp_code = input("Enter OTP: ")
+token = client.auth.verify_otp(otp_code, verify_id)
+print(f"Your Token is: {token}")
+client.set_token(token)
+
+song = client.music.get_song(6200)
+file_path = client.music.download_song(song['url_original'])
+print(f"\nDownload completed successfully!")
+print(f"File saved to: {file_path}")
+client.close()