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/recentlyPlayed.ts

@@ -0,0 +1,42 @@
+import { player, toQueueItems, type ApiTrackLike, type QueueItem } from '$lib/player/player.svelte';
+
+/**
+ * Merges the in-memory session history (tracks played since the page loaded)
+ * with the server-side listening history, de-duplicated by id and capped at `limit`.
+ */
+export function mergeRecentlyPlayed(history: ApiTrackLike[], limit: number): QueueItem[] {
+	const seen = new Set<string>();
+	const merged: QueueItem[] = [];
+
+	for (const t of player.recentlyPlayed) {
+		const id = String(t.id);
+		if (seen.has(id)) continue;
+		seen.add(id);
+		merged.push({
+			id,
+			title: t.title,
+			artist: t.artist,
+			source: t.source,
+			coverUrl: t.coverUrl,
+			explicit: t.explicit,
+			ownerUserId: t.ownerUserId
+		});
+	}
+
+	for (const item of toQueueItems(history)) {
+		const id = String(item.id);
+		if (seen.has(id)) continue;
+		seen.add(id);
+		merged.push({
+			id,
+			title: item.title,
+			artist: item.artist,
+			source: item.source ?? 'local',
+			coverUrl: item.coverUrl,
+			explicit: item.explicit,
+			ownerUserId: item.ownerUserId
+		});
+	}
+
+	return merged.slice(0, limit);
+}