add PWA support

sw.js

@@ -0,0 +1,59 @@
+const CACHE_NAME = 'ground-scanner-v1';
+const ASSETS_TO_CACHE = [
+  '/',
+  '/index.html',
+  '/manifest.json',
+  '/icon-192.png',
+  '/icon-512.png'
+];
+
+// Install - cache assets
+self.addEventListener('install', (event) => {
+  event.waitUntil(
+    caches.open(CACHE_NAME).then((cache) => {
+      return cache.addAll(ASSETS_TO_CACHE);
+    })
+  );
+  self.skipWaiting();
+});
+
+// Activate - clean old caches
+self.addEventListener('activate', (event) => {
+  event.waitUntil(
+    caches.keys().then((cacheNames) => {
+      return Promise.all(
+        cacheNames
+          .filter((name) => name !== CACHE_NAME)
+          .map((name) => caches.delete(name))
+      );
+    })
+  );
+  self.clients.claim();
+});
+
+// Fetch - network first, fallback to cache
+self.addEventListener('fetch', (event) => {
+  // Skip non-GET requests
+  if (event.request.method !== 'GET') return;
+  
+  // Skip API calls (always fetch from network)
+  if (event.request.url.includes('api.hotspots.fabio.ovh')) return;
+  
+  event.respondWith(
+    fetch(event.request)
+      .then((response) => {
+        // Clone and cache successful responses
+        if (response.status === 200) {
+          const responseClone = response.clone();
+          caches.open(CACHE_NAME).then((cache) => {
+            cache.put(event.request, responseClone);
+          });
+        }
+        return response;
+      })
+      .catch(() => {
+        // Fallback to cache
+        return caches.match(event.request);
+      })
+  );
+});