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).

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>

frontend/src/lib/components/Navbar.svelte

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+<script lang="ts">
+	const links = [
+		{ href: '/', label: 'Inicio' },
+		{ href: '/explore', label: 'Explorar' }
+	];
+</script>
+
+<header class="sticky top-0 z-50 border-b border-white/5 bg-neutral-950/80 backdrop-blur">
+	<nav class="mx-auto flex max-w-6xl items-center justify-between px-6 py-4">
+		<a href="/" class="flex items-center gap-2 text-lg font-bold tracking-tight">
+			<span class="grid h-8 w-8 place-items-center rounded-lg bg-emerald-500 text-neutral-950">♪</span>
+			Musify
+		</a>
+
+		<div class="hidden items-center gap-8 md:flex">
+			{#each links as link (link.href)}
+				<a href={link.href} class="text-sm text-neutral-300 transition hover:text-white">{link.label}</a>
+			{/each}
+		</div>
+
+		<div class="flex items-center gap-3">
+			<a href="/login" class="text-sm font-medium text-neutral-300 transition hover:text-white">
+				Iniciar sesión
+			</a>
+			<a
+				href="/login"
+				class="rounded-full bg-emerald-500 px-4 py-2 text-sm font-semibold text-neutral-950 transition hover:bg-emerald-400"
+			>
+				Registrarse
+			</a>
+		</div>
+	</nav>
+</header>