feat(download): switch download buttons to direct source links

The token relay still stood between the button and the file: every click
issued a short-lived token URL, so downloads never reached the real
source address directly.

- Render direct anchors (target=_blank) to the raw source URL in the
  download box and the paid card, with inline extract-code buttons
- Retire the relay: delete Content\Download plus its init wiring, header
  query-var branch and SEO noindex branch, and drop the dead
  download-request flow from cms-download.js (cashier, scan-pay and
  error views stay)
- Keep the dl_token table and the download logs page as read-only
  history; unscheduling of the orphaned cleanup cron is preserved

functions.php

@@ -218,9 +218,6 @@ if (class_exists('AKSRT\\Payment\\CommissionLedger')) {
 if (class_exists('AKSRT\\Payment\\InviteCode')) {
     \AKSRT\Payment\InviteCode::get_instance()->init();
 }
-if (class_exists('\AKSRT\Content\Download')) {
-    \AKSRT\Content\Download::get_instance()->init();
-}
 if (class_exists('\AKSRT\Content\Pay')) {
     \AKSRT\Content\Pay::get_instance()->init();
 }