feat (workflow): Video Sourcing + Retouch – 下载病毒片段,取出密钥框,retouch,通过Telegram审查,再上传

VideoSourcing(fp_profile_path)
  ├── download_video(source_url) → local MP4 path
  ├── extract_key_frames(video_path, count=6) → List[FrameInfo]
  ├── analyze_frames(frames) → AI analysis of best moments
  ├── retouch_video(video_path, instructions) → retouched MP4 path
  ├── generate_slider_from_frames(frames, concept) → slider pack
  └── run(source_item) → DraftContent