Frontend: /engines index + /engines/:slug detail routes, nav menu item and
en/hu translations. Engine pages are few, so the index uses an emphasized
poster-style design (dark slate, emerald accents, numbered full-width cards
with content preview) instead of the blog/howtos layouts. Slugs are the last
wiki path segment, since engine pages live scattered in the wiki tree.
API: /api/rss/engines feed linking to the site's engine pages, and a
WikiService#pages alias for #index — RssService called the alias-less name,
so the blog and howtos feeds were raising NoMethodError.