PWA: install button, one icon badge for Signal, mail and tasks due, share target for files, manifest launch handler

Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>

public/boot.js

@@ -22,7 +22,9 @@
   addEventListener('hashchange', route);
   restorePlayer();
   route();
+  shareCheck();
   mailPoll(); setInterval(mailPoll, 2 * 60e3);
+  taskPoll(); setInterval(taskPoll, 10 * 60e3);
   if ('serviceWorker' in navigator) navigator.serviceWorker.register('/sw.js').catch(() => {});
 })();