chore: add 404 page and remove unused boilerplate SVGs

- Add src/app/not-found.tsx with branded 404 design matching dark theme
- Remove unused Next.js boilerplate: file.svg, globe.svg, next.svg, vercel.svg, window.svg

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

Author: JoeMatt

public/file.svg

@@ -0,0 +1,36 @@
+import type { Metadata } from 'next';
+import Link from 'next/link';
+
+export const metadata: Metadata = {
+  title: '404 – Page Not Found',
+  description: 'The page you were looking for could not be found.',
+  robots: { index: false, follow: false },
+};
+
+export default function NotFound() {
+  return (
+    <div className="min-h-screen bg-gray-950 flex items-center justify-center px-4">
+      <div className="max-w-md mx-auto text-center">
+        <div className="text-8xl font-black text-orange-500 mb-4">404</div>
+        <h1 className="text-2xl font-bold text-white mb-3">Page Not Found</h1>
+        <p className="text-gray-400 mb-8">
+          The page you&apos;re looking for doesn&apos;t exist or has been moved.
+        </p>
+        <div className="flex flex-col sm:flex-row gap-3 justify-center">
+          <Link
+            href="/"
+            className="bg-orange-700 hover:bg-orange-600 text-white px-6 py-3 rounded-xl font-semibold transition-colors"
+          >
+            Go Home
+          </Link>
+          <Link
+            href="/downloads/"
+            className="bg-gray-800 hover:bg-gray-700 text-white px-6 py-3 rounded-xl font-semibold transition-colors border border-gray-700"
+          >
+            Downloads
+          </Link>
+        </div>
+      </div>
+    </div>
+  );
+}