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/NowPlaying.svelte

@@ -5,19 +5,14 @@
 
 	let { paused = false }: Props = $props();
 
-	const bars = [
-		{ delay: 0, dur: 0.9 },
-		{ delay: 0.25, dur: 0.7 },
-		{ delay: 0.1, dur: 1.05 },
-		{ delay: 0.4, dur: 0.8 }
-	];
+	const delays = [0, 0.3, 0.6];
 </script>
 
-<div class="absolute inset-0 flex items-end justify-center gap-[2.5px] bg-scrim/45 pb-2">
-	{#each bars as bar, i (i)}
+<div class="absolute inset-0 flex items-end justify-center gap-[3px] bg-scrim/45 pb-2.5">
+	{#each delays as delay (delay)}
 		<span
 			class="w-[3px] origin-bottom rounded-full bg-on-art"
-			style="height:14px; animation:equalize {bar.dur}s ease-in-out {bar.delay}s infinite; animation-play-state:{paused
+			style="height:14px; animation:equalize .9s ease-in-out {delay}s infinite; animation-play-state:{paused
 				? 'paused'
 				: 'running'}"
 		></span>