- Moved generate_thumbnail() and thumbnails().set() to run after video upload
- Now waits for video_id before attempting thumbnail upload
- Applies only to widescreen videos (Shorts still skip thumbnails)
- Integrated generate_thumbnail() into upload_video()
- Attempted to upload custom thumbnail via thumbnails().set()
- Applies only to widescreen videos (not vertical Shorts)
- NOTE: Bug present — tries to upload thumbnail before video_id is available
- Will fix by reordering after upload in next commit
