feat: pwa manifest, icon and minimal service worker

web/public/sw.js

@@ -0,0 +1,11 @@
+self.addEventListener('install', () => {
+  self.skipWaiting()
+})
+
+self.addEventListener('activate', (event) => {
+  event.waitUntil(self.clients.claim())
+})
+
+self.addEventListener('fetch', () => {
+  // no-op: presence of a fetch handler enables PWA install
+})