refactor: rename frontend/ to web-player/ and format with prettier

Updates the compose build context, the Dockerfile header, the package
name and the docs. The compose service and container keep the name
frontend/musify-frontend, since nginx routes to http://frontend:3000.

The source files also carry the first prettier pass, so the rename and
the reformat land together for them.

web-player/src/routes/api/tracks/+server.ts

@@ -0,0 +1,15 @@
+import type { RequestHandler } from './$types';
+import { json } from '@sveltejs/kit';
+import { createApiClient, unwrapOrError } from '$lib/server/api';
+import { EXPLORE_PAGE_SIZE } from '$lib/config';
+
+export const GET: RequestHandler = async ({ url, locals, fetch }) => {
+	const name = url.searchParams.get('name')?.trim() || undefined;
+	const pageNumber = Math.max(1, Number(url.searchParams.get('pageNumber')) || 1);
+	const pageSize = Math.max(1, Number(url.searchParams.get('pageSize')) || EXPLORE_PAGE_SIZE);
+
+	const api = createApiClient({ fetch, accessToken: locals.accessToken ?? undefined });
+	const result = await api.GET('/tracks', { params: { query: { name, pageNumber, pageSize } } });
+
+	return json(unwrapOrError(result, 'No se pudieron cargar las canciones.'));
+};