fix: PWA install prompt - add PNG icons and fix apple-touch-icon

Browsers require PNG icons (192x192, 512x512) in the manifest to show
the install prompt. SVG-only manifests are not sufficient. Also adds the
180x180 apple-touch-icon PNG for iOS home screen, bumps SW cache to v3,
and adds scope to the manifest.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

static/sw.js

@@ -1,22 +1,22 @@
-/* INTERCEPT Service Worker — cache-first static, network-only for API/SSE/WS */
-const CACHE_NAME = 'intercept-v2';
-
-const NETWORK_ONLY_PREFIXES = [
-    '/stream', '/ws/', '/api/', '/gps/', '/wifi/', '/bluetooth/',
-    '/adsb/', '/ais/', '/acars/', '/aprs/', '/tscm/', '/satellite/',
-    '/meshtastic/', '/bt_locate/', '/receiver/', '/sensor/', '/pager/',
-    '/sstv/', '/weather-sat/', '/subghz/', '/rtlamr/', '/dsc/', '/vdl2/',
+/* INTERCEPT Service Worker — cache-first static, network-only for API/SSE/WS */
+const CACHE_NAME = 'intercept-v3';
+
+const NETWORK_ONLY_PREFIXES = [
+    '/stream', '/ws/', '/api/', '/gps/', '/wifi/', '/bluetooth/',
+    '/adsb/', '/ais/', '/acars/', '/aprs/', '/tscm/', '/satellite/',
+    '/meshtastic/', '/bt_locate/', '/receiver/', '/sensor/', '/pager/',
+    '/sstv/', '/weather-sat/', '/subghz/', '/rtlamr/', '/dsc/', '/vdl2/',
     '/spy/', '/space-weather/', '/websdr/', '/analytics/', '/correlation/',
     '/recordings/', '/controller/', '/ops/',
 ];
-
-const STATIC_PREFIXES = [
-    '/static/css/',
-    '/static/js/',
-    '/static/icons/',
-    '/static/fonts/',
-];
-
+
+const STATIC_PREFIXES = [
+    '/static/css/',
+    '/static/js/',
+    '/static/icons/',
+    '/static/fonts/',
+];
+
 const CACHE_EXACT = ['/manifest.json'];
 
 function isHttpRequest(req) {
@@ -29,9 +29,9 @@ function isNetworkOnly(req) {
     const accept = req.headers.get('Accept') || '';
     if (accept.includes('text/event-stream')) return true;
     const url = new URL(req.url);
-    return NETWORK_ONLY_PREFIXES.some(p => url.pathname.startsWith(p));
-}
-
+    return NETWORK_ONLY_PREFIXES.some(p => url.pathname.startsWith(p));
+}
+
 function isStaticAsset(req) {
     const url = new URL(req.url);
     if (CACHE_EXACT.includes(url.pathname)) return true;
@@ -62,19 +62,19 @@ function fallbackResponse(req, status = 503) {
         headers: { 'Content-Type': 'text/plain; charset=utf-8' },
     });
 }
-
-self.addEventListener('install', (e) => {
-    self.skipWaiting();
-});
-
-self.addEventListener('activate', (e) => {
-    e.waitUntil(
-        caches.keys().then(keys =>
-            Promise.all(keys.filter(k => k !== CACHE_NAME).map(k => caches.delete(k)))
-        ).then(() => self.clients.claim())
-    );
-});
-
+
+self.addEventListener('install', (e) => {
+    self.skipWaiting();
+});
+
+self.addEventListener('activate', (e) => {
+    e.waitUntil(
+        caches.keys().then(keys =>
+            Promise.all(keys.filter(k => k !== CACHE_NAME).map(k => caches.delete(k)))
+        ).then(() => self.clients.claim())
+    );
+});
+
 self.addEventListener('fetch', (e) => {
     const req = e.request;
 
@@ -90,18 +90,18 @@ self.addEventListener('fetch', (e) => {
         );
         return;
     }
-
-    // Cache-first for static assets
-    if (isStaticAsset(req)) {
-        e.respondWith(
-            caches.open(CACHE_NAME).then(cache =>
-                cache.match(req).then(cached => {
-                    if (cached) {
-                        // Revalidate in background
-                        fetch(req).then(res => {
-                            if (res && res.status === 200) cache.put(req, res.clone());
-                        }).catch(() => {});
-                        return cached;
+
+    // Cache-first for static assets
+    if (isStaticAsset(req)) {
+        e.respondWith(
+            caches.open(CACHE_NAME).then(cache =>
+                cache.match(req).then(cached => {
+                    if (cached) {
+                        // Revalidate in background
+                        fetch(req).then(res => {
+                            if (res && res.status === 200) cache.put(req, res.clone());
+                        }).catch(() => {});
+                        return cached;
                     }
                     return fetch(req).then(res => {
                         if (res && res.status === 200) cache.put(req, res.clone());
@@ -111,12 +111,12 @@ self.addEventListener('fetch', (e) => {
             )
         );
         return;
-    }
-
-    // Network-first for HTML pages
-    e.respondWith(
-        fetch(req).catch(() =>
-            caches.match(req).then(cached => cached || new Response('Offline', { status: 503 }))
-        )
-    );
-});
+    }
+
+    // Network-first for HTML pages
+    e.respondWith(
+        fetch(req).catch(() =>
+            caches.match(req).then(cached => cached || new Response('Offline', { status: 503 }))
+        )
+    );
+});