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)/albums/[id]/+page.server.ts

@@ -42,7 +42,7 @@ export const load: PageServerLoad = async ({ params, locals, url, fetch, parent
 		(track) => track.source === 'Local' && !inAlbum.has(track.id)
 	);
 
-	const isOwner = user !== null && Number(album.ownerUserId) === Number(user.sub);
+	const isOwner = user !== null && String(album.ownerUserId) === user.sub;
 
 	return { album, tracks, library, isOwner, section: isOwner ? '/albums' : null };
 };