Refactor code style and improve documentation

- Standardized string quotes to single quotes across all files.
- Added docstrings to several functions and classes for better clarity.
- Updated mypy configuration in pyproject.toml for enhanced type checking.
- Ignored specific linting rules for test files in ruff configuration.
- Improved error messages in exception handling for better user feedback.
- Cleaned up code formatting and structure for consistency.

main.py

@@ -3,9 +3,9 @@ from __future__ import annotations
 import sys
 from pathlib import Path
 
-sys.path.insert(0, str(Path(__file__).resolve().parent / "src"))
+sys.path.insert(0, str(Path(__file__).resolve().parent / 'src'))
 
 from yt_shorts_downloader.cli import main
 
-if __name__ == "__main__":
+if __name__ == '__main__':
     raise SystemExit(main())