Add comprehensive theme rules and update authentication UI

- Create complete design system with color palette, typography, and component rules
- Update authentication pages with consistent styling
- Add footer component for better layout structure
- Remove deprecated architecture documentation

💘 Generated with Crush
Co-Authored-By: 💘 Crush <crush@charm.land>

app/views/layouts/application.html.erb

@@ -28,6 +28,12 @@
       <%= render "components/header" %>
     </div><!-- /#header -->
 
-    <%= yield %>
+    <main>
+        <%= yield %>
+    </main>
+
+    <div id="footer">
+      <%= render "components/footer" %>
+    </div>
   </body>
 </html>