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

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

web-player/src/routes/(app)/albums/[id]/components/AlbumHeader.svelte

@@ -48,17 +48,17 @@
 	label={isOwner ? 'Volver a tus álbumes' : 'Volver al inicio'}
 />
 
-<div class="mt-5 flex flex-col gap-5 sm:mt-6 sm:flex-row sm:items-end sm:gap-6">
+<div class="mt-3 flex flex-col gap-5 sm:mt-4 sm:flex-row sm:items-end sm:gap-6">
 	<PlaylistArt
 		{trackIds}
 		{coverUrl}
 		size="large"
-		class="h-36 w-36 shrink-0 rounded-art-lg shadow-art-lg sm:h-44 sm:w-44"
+		class="h-36 w-36 shrink-0 rounded-[18px] shadow-[0_24px_56px_rgba(0,0,0,.55)] sm:h-41 sm:w-41"
 	/>
 	<div class="min-w-0 flex-1">
-		<p class="text-sm tracking-[0.14em] text-fg-3 uppercase">Álbum</p>
+		<p class="text-[10.5px] font-semibold tracking-[0.16em] text-fg-2 uppercase">Álbum</p>
 		<h1
-			class="mt-1.5 font-display text-3xl font-semibold tracking-tight break-words text-fg sm:text-5xl md:text-7xl"
+			class="mt-1.5 font-display text-[28px] font-semibold tracking-[-0.035em] break-words text-fg sm:text-[33px]"
 		>
 			{title}
 		</h1>
@@ -72,10 +72,10 @@
 <div class="mt-6 flex flex-wrap items-center gap-2.5 sm:mt-7">
 	<Button size="sm" onclick={onPlayAll} disabled={trackIds.length === 0}>
 		{#if playing}
-			<Pause class="h-4 w-4" fill="currentColor" strokeWidth={1.5} />
+			<Pause class="h-4 w-4" strokeWidth={1.5} />
 			Pausar
 		{:else}
-			<Play class="h-4 w-4" fill="currentColor" strokeWidth={1.5} />
+			<Play class="h-4 w-4" strokeWidth={1.5} />
 			Reproducir
 		{/if}
 	</Button>