feat: complete Week 1 frontend setup (#9 #10 #11 #12)

- Install and configure Tailwind CSS (#9)
- Install Nuxt UI component library (#10)
- Create app layout with header/footer components (#11)
- Implement Supabase client composable (#12)
- Add TypeScript database types
- Create placeholder pages (index, scan, settings)
- Setup responsive navigation with mobile menu
- Configure auth state management

All Week 1 frontend foundation tasks complete.

app/app/app.vue

@@ -1,6 +1,5 @@
 <template>
-  <div>
-    <NuxtRouteAnnouncer />
-    <NuxtWelcome />
-  </div>
+  <NuxtLayout>
+    <NuxtPage />
+  </NuxtLayout>
 </template>

app/app/layouts/default.vue

@@ -0,0 +1,15 @@
+<template>
+  <div class="min-h-screen bg-gray-50">
+    <AppHeader />
+    
+    <main class="container mx-auto px-4 py-6 max-w-7xl">
+      <slot />
+    </main>
+
+    <AppFooter />
+  </div>
+</template>
+
+<script setup lang="ts">
+// App layout automatically wraps all pages
+</script>