feat: add PWA manifest configuration (#32)

- Install @vite-pwa/nuxt module
- Configure PWA manifest with app metadata
- Set up Workbox service worker configuration
- Add runtime caching for Supabase API
- Enable PWA dev mode for testing
- Configure icons and screenshots (placeholders for #33)

Closes #32

app/nuxt.config.ts

@@ -5,7 +5,8 @@ export default defineNuxtConfig({
 
   modules: [
     '@nuxt/ui',
-    '@nuxt/fonts'
+    '@nuxt/fonts',
+    '@vite-pwa/nuxt'
   ],
 
   runtimeConfig: {
@@ -17,5 +18,102 @@ export default defineNuxtConfig({
 
   colorMode: {
     preference: 'light'
+  },
+
+  pwa: {
+    registerType: 'autoUpdate',
+    manifest: {
+      name: 'Pantry - Smart Inventory Manager',
+      short_name: 'Pantry',
+      description: 'Track your household pantry inventory with ease. Barcode scanning, smart organization, and multi-user support.',
+      theme_color: '#10b981',
+      background_color: '#ffffff',
+      display: 'standalone',
+      orientation: 'portrait',
+      scope: '/',
+      start_url: '/',
+      categories: ['productivity', 'lifestyle'],
+      icons: [
+        {
+          src: '/icon-192x192.png',
+          sizes: '192x192',
+          type: 'image/png',
+          purpose: 'any'
+        },
+        {
+          src: '/icon-512x512.png',
+          sizes: '512x512',
+          type: 'image/png',
+          purpose: 'any'
+        },
+        {
+          src: '/icon-192x192-maskable.png',
+          sizes: '192x192',
+          type: 'image/png',
+          purpose: 'maskable'
+        },
+        {
+          src: '/icon-512x512-maskable.png',
+          sizes: '512x512',
+          type: 'image/png',
+          purpose: 'maskable'
+        }
+      ],
+      screenshots: [
+        {
+          src: '/screenshot-mobile.png',
+          sizes: '390x844',
+          type: 'image/png',
+          form_factor: 'narrow',
+          label: 'Pantry inventory view on mobile'
+        },
+        {
+          src: '/screenshot-desktop.png',
+          sizes: '1920x1080',
+          type: 'image/png',
+          form_factor: 'wide',
+          label: 'Pantry inventory view on desktop'
+        }
+      ]
+    },
+    workbox: {
+      navigateFallback: '/',
+      globPatterns: ['**/*.{js,css,html,png,svg,ico}'],
+      cleanupOutdatedCaches: true,
+      runtimeCaching: [
+        {
+          urlPattern: /^https:\/\/api\.supabase\.co\/.*/i,
+          handler: 'NetworkFirst',
+          options: {
+            cacheName: 'supabase-api',
+            expiration: {
+              maxEntries: 100,
+              maxAgeSeconds: 60 * 60 * 24 // 24 hours
+            },
+            cacheableResponse: {
+              statuses: [0, 200]
+            }
+          }
+        },
+        {
+          urlPattern: /^https:\/\/.*\.supabase\.co\/.*/i,
+          handler: 'NetworkFirst',
+          options: {
+            cacheName: 'supabase-data',
+            expiration: {
+              maxEntries: 100,
+              maxAgeSeconds: 60 * 60 * 24 // 24 hours
+            },
+            cacheableResponse: {
+              statuses: [0, 200]
+            }
+          }
+        }
+      ]
+    },
+    devOptions: {
+      enabled: true,
+      type: 'module'
+    }
   }
 })