Add likes, follows and playlist visibility; redesign web-player UI

Backend:
- New Likes feature (toggle/get liked tracks) and endpoints
- User follow/unfollow, listening stats, public user profile
- Playlist visibility (public/private) support
- Various auth and DTO/response adjustments to support the above

Frontend (web-player):
- New design system pass: theme tokens/mode (light/dark), glass menu,
  tabs bar, player dock/extras/queue components, mix tiles, artist link
- New routes: Liked, public user profile (/u/[id]), likes API proxy
- Search refactor: shared SearchBox component used by TopBar and
  MobileHeader (search now reachable on mobile), live results as you
  type instead of requiring Enter, dropped the "Buscando…" quick-result
  preview
- Removed now-unused components (MobileNav, CoverBadge, MixBentoTile,
  PlayPauseOverlay, SuggestionsTable, userDirectory)
- Design handoff reference docs added under web-player/design_handoff_musify_player
  and web-player/docs/design-system-refactor-plan.md

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

@@ -4,19 +4,22 @@
 	import { trackTableKey, type TrackTableContext } from './TrackTable.svelte';
 
 	interface Props {
+		active?: boolean;
 		class?: string;
 		oncontextmenu?: (event: MouseEvent) => void;
 		children: Snippet;
 	}
 
-	let { class: klass = '', oncontextmenu, children }: Props = $props();
+	let { active = false, class: klass = '', oncontextmenu, children }: Props = $props();
 
 	const table = getContext<TrackTableContext>(trackTableKey);
 </script>
 
 <!-- svelte-ignore a11y_no_static_element_interactions -->
 <div
-	class="group grid track-grid items-center gap-3 rounded-control py-2.5 pr-4 pl-2 transition hover:bg-surface sm:gap-8 sm:pr-6 sm:pl-3 {klass}"
+	class="group grid track-grid items-center gap-3 rounded-control py-3 pr-4 pl-2 transition-colors sm:gap-8 sm:pr-6 sm:pl-3 {active
+		? 'bg-accent-tint'
+		: 'hover:bg-white/[3.2%]'} {klass}"
 	style="--mf-track-cols:{table.columns}; --mf-track-cols-mobile:{table.columnsMobile}"
 	{oncontextmenu}
 >