- Add BackgroundUploadManager class for managing uploads in background
- Create background upload button and panel UI
- Implement upload state transfer when modal closes
- Add real-time progress tracking for background uploads
- Support up to 5 concurrent uploads
- Display upload progress with percentage and chunk info
- Auto-hide background UI when all uploads complete
- Add responsive design for background panel
- Implement chunked file upload with 1MB chunk size
- Add progress bar with percentage and chunk counter (e.g., 2/5)
- Support resuming interrupted uploads
- Improve UI with better progress visualization
- Add dropzone.js integration for drag-and-drop uploads
- Fix progress bar jumping issue in resumable uploads
- Add file type icons and size display
- Enhance error handling and user feedback
