Enhance playlist functionality with improved error handling and official playlist support

[LeonKohli]

Thank you for creating and maintaining this excellent Spotify playlist tool! I've found it very useful and wanted to contribute some enhancements that make it even better.

This PR enhances the playlist functionality with the following improvements:

• Added "user-library-modify" scope to allow modifying saved tracks
• Enhanced playlist template with support for owner_id and is_official fields
• Improved track processing with robust error handling for unusual track structures
• Added support for podcast episodes
• Enhanced export functionality with error handling and owner detection
• Updated import functionality with:
  • Specialized handling for saved tracks
  • Option to follow official playlists instead of creating copies
  • Improved user interaction and feedback
  • Better error handling throughout

These changes maintain backward compatibility while adding new features to improve the reliability and user experience of the tool.