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/+layout.server.ts

@@ -1,8 +1,44 @@
 import { redirect } from '@sveltejs/kit';
 import type { LayoutServerLoad } from './$types';
 import { getAllowAnonymousListening } from '$lib/server/playbackConfig';
+import { createApiClient } from '$lib/server/api';
+import { authConfig } from '$lib/server/config';
+import { LIKED_TRACKS_PAGE_SIZE } from '$lib/config';
 
 const PUBLIC_PATHS = new Set(['/login']);
+const SIDEBAR_PLAYLISTS_LIMIT = 8;
+
+async function fetchSidebarPlaylists(
+	fetchFn: typeof fetch,
+	accessToken: string | null,
+	userId: string
+) {
+	try {
+		const api = createApiClient({ fetch: fetchFn, accessToken: accessToken ?? undefined });
+		const { data } = await api.GET('/playlists/users/{userId}', {
+			params: {
+				path: { userId },
+				query: { pageNumber: 1, pageSize: SIDEBAR_PLAYLISTS_LIMIT }
+			}
+		});
+		return data?.items ?? [];
+	} catch {
+		// The sidebar shell must render even when the API is unreachable.
+		return [];
+	}
+}
+
+async function fetchLikedTracks(fetchFn: typeof fetch, accessToken: string | null) {
+	try {
+		const api = createApiClient({ fetch: fetchFn, accessToken: accessToken ?? undefined });
+		const { data } = await api.GET('/likes', {
+			params: { query: { pageNumber: 1, pageSize: LIKED_TRACKS_PAGE_SIZE } }
+		});
+		return data?.items ?? [];
+	} catch {
+		return [];
+	}
+}
 
 export const load: LayoutServerLoad = async ({ locals, url, fetch }) => {
 	const allowAnonymousListening = await getAllowAnonymousListening(fetch);
@@ -10,5 +46,31 @@ export const load: LayoutServerLoad = async ({ locals, url, fetch }) => {
 	if (!locals.user && !allowAnonymousListening && !PUBLIC_PATHS.has(url.pathname)) {
 		redirect(302, `/login?returnTo=${encodeURIComponent(url.pathname + url.search)}`);
 	}
-	return { user: locals.user, allowAnonymousListening };
+
+	const accountUrl = authConfig.issuer
+		? `${authConfig.issuer.replace(/\/+$/, '')}/ui/console`
+		: null;
+
+	if (!locals.user) {
+		return {
+			user: locals.user,
+			allowAnonymousListening,
+			sidebarPlaylists: [],
+			likedTracks: [],
+			accountUrl
+		};
+	}
+
+	const [sidebarPlaylists, likedTracks] = await Promise.all([
+		fetchSidebarPlaylists(fetch, locals.accessToken, locals.user.sub),
+		fetchLikedTracks(fetch, locals.accessToken)
+	]);
+
+	return {
+		user: locals.user,
+		allowAnonymousListening,
+		sidebarPlaylists,
+		likedTracks,
+		accountUrl
+	};
 };