feat(web): card hover-reveal + drop year + accent rule on section headers

First wave of Home visual polish (UI tasks 78/79/81/85):

- CardActionCluster like/queue/menu cluster is now opacity-0 and fades
  in on group-hover or focus-within. The group class moves from the
  inner anchor to the outer card wrapper so the cluster (positioned
  outside the anchor) participates in the same hover scope. PlaylistCard
  refresh kebab gets the same treatment.
- AlbumCard drops the year line. Title plus artist is enough on Home
  tiles; the album detail page still shows the year.
- HorizontalScrollRow h2 picks up a flex-baseline layout with a trailing
  12-wide accent rule (after:bg-accent/60), so section headers read as
  chapter breaks instead of identical plain text.
- AlbumCard art-wrap is shadow-sm by default and lifts to shadow-lg
  plus ring-accent/40 on hover. Pairs with the existing
  group-hover:scale-1.03 for a clean lift-on-mouseover feel.

web/src/lib/components/ArtistCard.svelte

@@ -42,10 +42,10 @@
   }
 </script>
 
-<div class="card relative">
+<div class="card group relative">
   <a
     href={`/artists/${artist.id}`}
-    class="group block rounded focus-visible:ring-2 focus-visible:ring-accent"
+    class="block rounded focus-visible:ring-2 focus-visible:ring-accent"
   >
     <div class="art-wrap relative mx-auto aspect-square w-full overflow-hidden rounded-full bg-surface-hover">
       {#if artist.cover_url}