feat(ui): add wedding theme styles and layout components

* Introduced wedding-themed CSS variables for styling.
* Created layout component for the wedding site with navigation and countdown.
* Added RSVP and photo upload pages with form handling.
* Implemented QR code page for wedding site access.
* Configured TypeScript and Vite for the project.
* Added robots.txt for search engine crawling.

ui/src/routes/+layout.svelte

@@ -0,0 +1,45 @@
+<script lang="ts">
+	import '../app.css';
+	import favicon from '$lib/assets/favicon.svg';
+	import { page } from '$app/state';
+	import Countdown from '$lib/components/Countdown.svelte';
+	import { createWeddingInfo } from '$lib/wedding-info.svelte';
+
+	let { children } = $props();
+
+	const wedding = createWeddingInfo();
+
+	const links = [
+		{ href: '/', label: 'Home' },
+		{ href: '/rsvp', label: 'RSVP' },
+		{ href: '/photos', label: 'Photos' }
+	];
+</script>
+
+<svelte:head><link rel="icon" href={favicon} /></svelte:head>
+
+<div class="bg-surface-50 dark:bg-surface-950 flex min-h-screen flex-col">
+	<div class="sticky top-0 z-20 flex flex-col">
+		<nav class="bg-primary-950 flex items-center justify-between px-4 py-3 sm:px-8">
+			<a href="/" class="text-surface-50 font-malibu text-xl tracking-wide">Zoé &amp; Shaldon</a>
+			<div class="flex gap-2">
+				{#each links as link (link.href)}
+					<a
+						href={link.href}
+						class="btn field-sm {page.url.pathname === link.href
+							? 'preset-filled-secondary-500'
+							: 'text-surface-100 hover:text-secondary-400'}"
+					>
+						{link.label}
+					</a>
+				{/each}
+			</div>
+		</nav>
+		<div class="text-surface-50 flex justify-center px-4 py-3 drop-shadow-[0_2px_6px_rgba(0,0,0,0.6)]">
+			<Countdown target={wedding.date} compact pastMessage="Already married! 🎉" />
+		</div>
+	</div>
+	<main class="flex flex-1 flex-col">
+		{@render children()}
+	</main>
+</div>