feat: in-reader settings, more like this, reading history, audio filter, feed page

- Add floating gear button + theme/font/size drawer in chapter reader
- Add 'More like this' horizontal scroll row on book detail page
- Add reading history tab on profile page (chronological progress timeline)
- Add audio-available badge + filter toggle on catalogue (GET /api/audio/slugs)
- Fix discover card entry animation pop (split entry vs snap-back cubic-bezier)
- Add dedicated /feed page showing books followed users are reading
- Add Feed nav link (desktop + mobile) in all 5 locales

ui/messages/en.json

@@ -3,6 +3,7 @@
 
   "nav_library": "Library",
   "nav_catalogue": "Catalogue",
+  "nav_feed": "Feed",
   "nav_feedback": "Feedback",
   "nav_admin": "Admin",
   "nav_profile": "Profile",
@@ -419,5 +420,16 @@
   "profile_text_size_sm": "Small",
   "profile_text_size_md": "Normal",
   "profile_text_size_lg": "Large",
-  "profile_text_size_xl": "X-Large"
+  "profile_text_size_xl": "X-Large",
+
+  "feed_page_title": "Feed — LibNovel",
+  "feed_heading": "Following Feed",
+  "feed_subheading": "Books your followed users are reading",
+  "feed_empty_heading": "Nothing here yet",
+  "feed_empty_body": "Follow other readers to see what they're reading.",
+  "feed_not_logged_in": "Sign in to see your feed.",
+  "feed_reader_label": "reading",
+  "feed_chapters_label": "{n} chapters",
+  "feed_browse_cta": "Browse catalogue",
+  "feed_find_users_cta": "Discover readers"
 }