feat(web): dominant-color accent strip on PlayerBar + bigger Home tiles

#9 — new lib/media/dominantColor.ts: load cover image, downsample to
1x1 canvas, read pixel. Approximates the dominant tone via the
browser's bilinear mean — close enough for an ambient accent without
the 5KB ColorThief dependency. Same-origin cover URLs so no CORS
dance. Result cached by URL so revisits are free.

PlayerBar samples the current track's cover and pipes the resulting
rgb into a 2px accent strip above both the compact and desktop
variants. Transparent until the first resolve; 300ms transition on
colour change so track-skips fade rather than snap.

#10 — slight bump to Home tile widths so a typical viewport shows
roughly 5-6 across instead of cramming 8-9: Playlists w-56, all
remaining AlbumCard rows w-48 (Recently Added + both Rediscover
album scrollers). Replaces the wave-2 sizes that were still showing
7-8 across on wider screens.

web/src/routes/+page.svelte

@@ -143,8 +143,9 @@
     >
       {#snippet item(rowItem: PlaylistRowItem)}
         <!-- Playlists at the page anchor: largest of the carousels.
-             Recently added stays at w-44; Rediscover steps down. -->
-        <div class="w-52">
+             Sized so a typical viewport shows ~5-6 across instead
+             of cramming 8-9. -->
+        <div class="w-56">
           {#if rowItem.kind === 'real'}
             <PlaylistCard playlist={rowItem.playlist} />
           {:else}
@@ -174,7 +175,7 @@
           ariaLabel="Recently added"
         >
           {#snippet item(album: import('$lib/api/types').AlbumRef)}
-            <div class="w-44"><AlbumCard {album} /></div>
+            <div class="w-48"><AlbumCard {album} /></div>
           {/snippet}
         </HorizontalScrollRow>
       {/if}