Add common header and footer

Implement a common header and footer for all pages except interactive pages. The footer will initially contain placeholder text.

src/pages/Themes.tsx

@@ -8,7 +8,7 @@ import {
   CreditCard,
   Calculator
 } from "lucide-react";
-import Navigation from "@/components/Navigation";
+import Layout from "@/components/Layout";
 import ThemeCard from "@/components/ThemeCard";
 
 const Themes = () => {
@@ -58,8 +58,7 @@ const Themes = () => {
   ];
 
   return (
-    <div className="min-h-screen bg-background">
-      <Navigation />
+    <Layout>
       
       <div className="py-12 px-4">
         <div className="max-w-6xl mx-auto">
@@ -78,7 +77,7 @@ const Themes = () => {
 
         </div>
       </div>
-    </div>
+    </Layout>
   );
 };