refactored templates

app/templates/centered_layout.html

@@ -0,0 +1,13 @@
+{% extends "base.html" %}
+
+{# Centered card layout used by login, register, and set_token pages. #}
+
+{% block body_class %}flex items-center justify-center min-h-screen bg-background{% endblock %}
+
+{% block body %}
+  <div class="bg-gray-800 p-8 rounded-lg shadow-lg max-w-md w-full border border-gray-700">
+    {% block card_content %}{% endblock %}
+  </div>
+{% endblock %}
+
+{% block scripts %}{% endblock %}{# No Flowbite needed on auth pages #}