WIP: Architecture Refactor, add stub files and working blog post wrapped by AppShell

src/frontend/pages/not-found.tsx

@@ -0,0 +1,9 @@
+import React from 'react';
+
+export function NotFound() {
+    return (
+        <main>
+            <h1>404 Not Found</h1>
+        </main>
+    )
+}