Refactored frontend + added template engine

frontend/templates/404.html

@@ -0,0 +1,17 @@
+{% extends "base.html" %}
+{% block title %}404 - Not Found{% endblock %}
+
+{% block content %}
+<div class="flex flex-col items-center justify-center text-center px-4 py-16">
+  <div class="max-w-xl">
+    <h1 class="text-7xl font-extrabold text-blue-600 mb-6">404</h1>
+    <h2 class="text-3xl font-bold text-gray-800 mb-4">Oops, we couldn’t find that page!</h2>
+    <p class="text-gray-600 mb-8">
+      It seems DocuNova has misplaced the document you were looking for. Don’t worry – we’ve got your back.
+    </p>
+    <a href="/" class="inline-block bg-blue-500 hover:bg-blue-600 text-white font-semibold py-3 px-6 rounded-lg transition-colors">
+      &larr; Return Home
+    </a>
+  </div>
+</div>
+{% endblock %}