feat: add create and message page UI

Co-authored-by: 이지은 <ijieun@ijieun-ui-MacBookPro.local>

src/routes/create/+page.svelte

@@ -1 +1,42 @@
-<h1>/create page</h1>
+<script>
+	import Header from '$lib/components/ui/Header.svelte';
+	import Artwork from '$lib/components/ui/Artwork/Artwork.svelte';
+	import ContextForm from '$lib/components/ui/create/ContextForm.svelte';
+
+	let who = $state(null);
+	let whatFor = $state(null);
+	let style = $state(null);
+	let budget = $state(50_000);
+
+	const hasAnySelection = $derived(who !== null || whatFor !== null || style !== null);
+
+	const artworkTitle = $derived.by(() => {
+		if (!hasAnySelection) return 'Title';
+		const occasion = whatFor ? `A ${whatFor} bouquet for` : 'A bouquet for';
+		return `${occasion} ${who ?? '...'}`;
+	});
+
+	const artworkDescription = $derived(
+		hasAnySelection
+			? `${style ?? '—'} style · ₩${budget.toLocaleString('ko-KR')} budget`
+			: 'Description Description Description'
+	);
+</script>
+
+<!--
+	upload와 같은 2열 레이아웃: 좌측 Artwork 고정, 우측 ContextForm.
+	선택값이 바뀌면 create1 → create2 헤드라인·요약이 반응형으로 전환됩니다.
+-->
+<div
+	class="flex h-dvh flex-col overflow-x-hidden bg-surface text-ink lg:h-screen lg:overflow-hidden"
+>
+	<Header step={1} total={6} />
+
+	<main class="flex min-h-0 flex-1 flex-col lg:flex-row">
+		<Artwork title={artworkTitle} description={artworkDescription} />
+
+		<section class="relative flex min-h-0 flex-1 flex-col lg:overflow-y-auto">
+			<ContextForm bind:who bind:whatFor bind:style bind:budget />
+		</section>
+	</main>
+</div>