Refactor code structure for improved readability and maintainability

main.py

@@ -1,3 +1,10 @@
+from __future__ import annotations
+
+import sys
+from pathlib import Path
+
+sys.path.insert(0, str(Path(__file__).resolve().parent / "src"))
+
 from yt_shorts_downloader.cli import main
 
 if __name__ == "__main__":