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/routes/(app)/library/+page.svelte

@@ -51,20 +51,28 @@
 			index
 			action
 			meta={[
+				{ label: 'Álbum', width: '160px' },
 				{ label: 'Subida', width: '100px' },
 				{ label: 'Escuchas', width: '100px' }
 			]}
-			class="mt-6 sm:mt-8"
+			class="mt-7 sm:mt-8"
 		>
 			{#each items as track, i (track.id)}
-				<TrackRow>
+				{@const active = player.current.id === track.id}
+				<TrackRow {active}>
 					<TrackIndexCell
 						index={i}
-						active={player.current.id === track.id}
+						{active}
 						playing={player.playing}
 						onToggle={() => togglePlay(i)}
 					/>
-					<TrackTitleCell trackId={track.id} title={track.title} onClick={() => togglePlay(i)} />
+					<TrackTitleCell
+						trackId={track.id}
+						title={track.title}
+						{active}
+						onClick={() => togglePlay(i)}
+					/>
+					<TrackMeta class="hidden sm:block">—</TrackMeta>
 					<TrackMeta class="hidden sm:block">{fmtDate(track.createdAt)}</TrackMeta>
 					<TrackMeta class="hidden sm:block">{Number(track.listensCount)}</TrackMeta>
 					<TrackMeta>{fmtTime(Number(track.duration))}</TrackMeta>