- Fix handleTagClick to unselect other tags when selecting new tag
- Add handlePlayButtonClick to move individual tagged files
- Add 'behind-the-scenes' tag support to main.js
- Map tag types to Jellyfin-compatible folder names
- Add comprehensive test coverage (24 new tests)
- Fix displayCreatedFolder folder name mapping issue
This implements the full tagging workflow: tag a file with extra/
behind-the-scenes/delete, then click play button to move it to the
appropriate folder.