Checkpoint web-player design-system refactor and backend track genre tagging

Advances the ongoing token/componentization cleanup (anchored player dock,
border-based panels instead of floating shadows, corrected light-mode
accent/gradient tokens) alongside in-progress backend support for track
genre tags.

web-player/src/lib/components/ui/MediaCard.svelte

@@ -1,6 +1,6 @@
 <script lang="ts" module>
 	export const mediaCardArt =
-		'aspect-square w-full rounded-art shadow-art transition duration-300 ease-out group-hover:shadow-art-lg';
+		'aspect-square w-full rounded-art transition duration-300 ease-out';
 </script>
 
 <script lang="ts">
@@ -25,7 +25,7 @@
 	{oncontextmenu}
 >
 	{@render art(mediaCardArt)}
-	<div class="mt-2.5 truncate text-sm font-medium text-fg">{title}</div>
+	<div class="mt-2.5 truncate text-fg">{title}</div>
 	{#if subtitle}
 		<div class="mt-0.5 truncate text-xs text-fg-3">{subtitle}</div>
 	{/if}