feat(home): add a "Recommended for you" shelf

Surface the content-based /me/recommendations feed as a horizontal shelf on
the homepage, below the Continue-reading shelf. Fetched after the catalogue
(same non-blocking pattern), shown only when signed in and the feed is
non-empty; reuses MangaCard in a fixed-width scroller. Component unit test +
e2e (signed-in shows cards, anonymous hides).

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

backend/Cargo.lock

@@ -1558,7 +1558,7 @@ checksum = "c41e0c4fef86961ac6d6f8a82609f55f31b05e4fce149ac5710e439df7619ba4"
 
 [[package]]
 name = "mangalord"
-version = "0.108.0"
+version = "0.109.0"
 dependencies = [
  "anyhow",
  "argon2",

backend/Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "mangalord"
-version = "0.108.0"
+version = "0.109.0"
 edition = "2021"
 default-run = "mangalord"