fix(pwa): switch service worker to network-first strategy

Cache-first was preventing updates from reaching users. Network-first
always fetches fresh content and only falls back to cache when offline.
Also bumps cache version to evict stale cache-first entries.

app/static/sw.js

@@ -1,8 +1,6 @@
-const CACHE = 'apoena-v1';
+const CACHE = 'apoena-v2';
-const PRECACHE = ['/', '/worker.js', '/manifest.json', '/icon.svg', '/icon-maskable.svg'];
 
 self.addEventListener('install', e => {
-  e.waitUntil(caches.open(CACHE).then(c => c.addAll(PRECACHE)));
   self.skipWaiting();
 });
 
@@ -21,7 +19,14 @@ self.addEventListener('fetch', e => {
   // Pass through API calls
   if (url.pathname === '/extract-audio') return;
 
+  // Network-first: always fetch fresh content, update cache, fall back offline
   e.respondWith(
-    caches.match(e.request).then(cached => cached || fetch(e.request))
+    fetch(e.request)
+      .then(res => {
+        const clone = res.clone();
+        caches.open(CACHE).then(c => c.put(e.request, clone));
+        return res;
+      })
+      .catch(() => caches.match(e.request))
   );
 });