feat(web): radial gradient + playlist title overlay + tile-size hierarchy

Second wave of Home visual polish (UI tasks 80/82/84):

- Shell main background gets a 1200x600 radial gradient at the top
  using color-mix on fs-iron so the page reads with subtle depth
  instead of as a flat slab.
- PlaylistCard moves the title onto the cover with a bottom-to-top
  gradient overlay. The server-generated 2x2 collage becomes mood
  texture; the Fraunces playlist name becomes the dominant element.
  Track count and refresh label stay below the art. Mirror albums
  shadow-sm/shadow-lg/ring-accent hover treatment on the art-wrap.
- Tile-size hierarchy: Playlists w-52, Recently added w-44,
  Rediscover w-40. Visual weight tapers as you scroll down the
  page so the freshest content reads as most important.

web/src/lib/components/PlaylistCard.svelte

@@ -149,7 +149,11 @@
     href={`/playlists/${playlist.id}`}
     class="group flex w-full flex-col items-start gap-2 rounded-md p-2 text-left hover:bg-surface-hover"
   >
-    <div class="art-wrap relative aspect-square w-full overflow-hidden rounded-md bg-surface-hover">
+    <div
+      class="art-wrap relative aspect-square w-full overflow-hidden rounded-md
+             bg-surface-hover shadow-sm transition-all duration-150
+             group-hover:shadow-lg group-hover:ring-1 group-hover:ring-accent/40"
+    >
       {#if playlist.cover_url}
         <img
           src={playlist.cover_url}
@@ -161,6 +165,23 @@
           <span class="text-xs">No tracks yet</span>
         </div>
       {/if}
+      <!-- Bottom-to-top gradient so the Fraunces title overlay below
+           is legible against any cover. The server's playlist cover
+           is often a 2x2 collage; the gradient mutes the collage so
+           the playlist NAME becomes the dominant element. -->
+      <div
+        class="pointer-events-none absolute inset-0 bg-gradient-to-t
+               from-black/85 via-black/40 to-transparent"
+      ></div>
+      <!-- Title burned in at the bottom of the cover. Two lines max;
+           ellipsis. Fraunces (font-display) so it reads as
+           branded/curated content rather than just metadata. -->
+      <div class="pointer-events-none absolute inset-x-0 bottom-0 p-3">
+        <div
+          class="font-display text-base font-medium leading-tight text-text-primary
+                 [display:-webkit-box] [-webkit-box-orient:vertical] [-webkit-line-clamp:2] overflow-hidden"
+        >{playlist.name}</div>
+      </div>
       <button
         type="button"
         aria-label={`Play ${playlist.name}`}
@@ -172,7 +193,6 @@
       </button>
     </div>
     <div class="w-full min-w-0">
-      <div class="truncate text-sm font-medium text-text-primary">{playlist.name}</div>
       <div class="truncate text-xs text-text-muted">
         {playlist.track_count} {playlist.track_count === 1 ? 'track' : 'tracks'}
         {#if !isOwn}

web/src/lib/components/Shell.svelte

@@ -135,7 +135,16 @@
     </div>
   </header>
 
-  <main class="overflow-y-auto p-4">
+  <!-- Subtle 1200x600 radial highlight at the top of the scroll
+       area fades the slate tone (fs-iron with alpha) into the
+       background. Adds depth so the page doesn't read as a flat
+       slab. color-mix lets the gradient theme-track in case the
+       palette token ever shifts. -->
+  <main
+    class="overflow-y-auto p-4"
+    style="background-image: radial-gradient(ellipse 1200px 600px at 50% -100px,
+      color-mix(in srgb, var(--fs-iron) 60%, transparent), transparent 70%);"
+  >
     {@render children?.()}
   </main>
 

web/src/routes/+page.svelte

@@ -142,7 +142,9 @@
       ariaLabel="Playlists"
     >
       {#snippet item(rowItem: PlaylistRowItem)}
-        <div class="w-44">
+        <!-- Playlists at the page anchor: largest of the carousels.
+             Recently added stays at w-44; Rediscover steps down. -->
+        <div class="w-52">
           {#if rowItem.kind === 'real'}
             <PlaylistCard playlist={rowItem.playlist} />
           {:else}
@@ -195,7 +197,9 @@
             ariaLabel="Rediscover albums"
           >
             {#snippet item(album: import('$lib/api/types').AlbumRef)}
-              <div class="w-44"><AlbumCard {album} /></div>
+              <!-- Rediscover steps down vs Recently added to make the
+                   tile-size hierarchy read top-to-bottom. -->
+              <div class="w-40"><AlbumCard {album} /></div>
             {/snippet}
           </HorizontalScrollRow>
         {/if}