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/tasks.js

@@ -99,6 +99,13 @@ function newListSheet(lists, list) {
   el.querySelectorAll('[data-rm]').forEach(b => b.onclick = () => confirmSheet('Delete list?', 'Its tasks are deleted too.', 'Delete', async () => { await jfetch('/api/tasks/lists/delete', { method: 'POST', body: JSON.stringify({ id: b.dataset.rm }) }); store.del('task_list'); viewTasks(); }));
 }
 
+// Overdue and due-today tasks, for the icon badge
+let taskDue = 0;
+async function taskPoll() {
+  if (!allowed('tasks')) return;
+  try { const s = await jfetch('/api/tasks/summary?today=' + ymd(new Date())), n = (s.overdue || 0) + (s.today || 0); if (n !== taskDue) { taskDue = n; renderNav(); } } catch {}
+}
+
 // Home: a card only when something is overdue or due today
 async function renderTasksCard(el) {
   if (!el) return;