[FA-misc] Astro migration works, probably want to touchup the frontend but that can be in Phase 4

fictionarchive-web-astro/src/pages/404.astro

@@ -0,0 +1,23 @@
+---
+export const prerender = true; // Static page
+
+import AppLayout from '../layouts/AppLayout.astro';
+import { Card, CardContent, CardHeader, CardTitle } from '../lib/components/ui/card';
+import { Button } from '../lib/components/ui/button';
+---
+
+<AppLayout title="Not Found - FictionArchive">
+	<div class="flex min-h-[50vh] items-center justify-center">
+		<Card class="mx-auto max-w-md text-center shadow-md shadow-primary/10">
+			<CardHeader>
+				<CardTitle class="text-4xl font-bold">404</CardTitle>
+			</CardHeader>
+			<CardContent class="space-y-4">
+				<p class="text-muted-foreground">
+					The page you're looking for doesn't exist or has been moved.
+				</p>
+				<Button href="/" variant="default">Go back home</Button>
+			</CardContent>
+		</Card>
+	</div>
+</AppLayout>