Add anonymous listening support and redesign web-player UI

Backend:
- Expose GET /config/playback so the frontend can detect whether
  anonymous listening is enabled without requiring auth
- Wire anonymous access through track streaming and YouTube resolve flows

Frontend:
- Allow browsing/listening without a session when the backend enables it
- Redesign Inicio, Sidebar and top bar with a new dark theme, typography,
  and layout (top bar with live quick-search, sticky/blurred on scroll)
- Populate Top música, Popular and Recomendados with real Musify +
  YouTube Music data instead of placeholders
- Various shape, spacing, color and animation refinements across the
  redesigned components

web-player/src/lib/server/playbackConfig.ts

@@ -0,0 +1,22 @@
+import { createApiClient } from '$lib/server/api';
+
+const CACHE_TTL_MS = 30_000;
+
+let cached: { allowAnonymousListening: boolean; expiresAt: number } | null = null;
+
+export async function getAllowAnonymousListening(fetchFn: typeof fetch): Promise<boolean> {
+	if (cached && cached.expiresAt > Date.now()) return cached.allowAnonymousListening;
+
+	try {
+		const api = createApiClient({ fetch: fetchFn });
+		const { data } = await api.GET('/config/playback');
+		const allowAnonymousListening = data?.allowAnonymousListening ?? false;
+
+		cached = { allowAnonymousListening, expiresAt: Date.now() + CACHE_TTL_MS };
+		return allowAnonymousListening;
+	} catch {
+		// The API being unreachable shouldn't take down every page in the app;
+		// fail closed (as if anonymous listening were off) and retry next time.
+		return false;
+	}
+}