feat(frontend): scaffold SvelteKit + Tailwind with landing (part 1)

New SvelteKit app in frontend/ (minimal template, TypeScript, TailwindCSS v4).
Adds the app shell (dark music theme navbar + footer) and a landing page with
hero and feature cards. CTAs point to /login and /explore (built in later parts).

Verified: production build succeeds and the page renders with Tailwind styles
applied (checked via preview).

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

frontend/src/lib/components/Footer.svelte

@@ -0,0 +1,11 @@
+<footer class="border-t border-white/5 py-8">
+	<div
+		class="mx-auto flex max-w-6xl flex-col items-center justify-between gap-4 px-6 text-sm text-neutral-500 sm:flex-row"
+	>
+		<p>© {new Date().getFullYear()} Musify · Streaming de música.</p>
+		<div class="flex gap-6">
+			<a href="/explore" class="transition hover:text-neutral-300">Explorar</a>
+			<a href="/login" class="transition hover:text-neutral-300">Entrar</a>
+		</div>
+	</div>
+</footer>