Retire the old EEC-based /gift reader-magnet pages

Neon Tan now ships via shop.michaelferrara.org/arc/neon-tan (bookshop's
ARC giveaway: single email field, gated download, tracked redemptions)
instead of these EEC-course-driven pages, which required first name as
well as email and served the epub from an ungated public bucket URL.

Old /gift and /gift-thanks paths still work via Caddy's path_redirects
(reground-infrastructure), so any existing bookmarks/emailed links keep
resolving to the new page instead of 404ing.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

content/_index.md

@@ -5,4 +5,4 @@ description: "TODO: one-line author bio/description"
 
 TODO: Michael's homepage copy goes here.
 
-Get a free short story: [download the reader magnet](/gift).
+Get a free short story: [download the reader magnet](https://shop.michaelferrara.org/arc/neon-tan).