refactor(library): extract download action to controller
New route: GET /library/article/{id}/download/{type}
Legacy URLs (?act=download&type=X&id=Y) redirect 301 in index.php.
Updated book.phtml to use new absolute URLs.
Removed unused del and download from includes dispatch.
Legacy URLs (?act=download&type=X&id=Y) redirect 301 in index.php.
Updated book.phtml to use new absolute URLs.
Removed unused del and download from includes dispatch.