Add self-hosted kids calendar app

Express + SQLite (node:sqlite, no native build step) family calendar:
parent accounts with household invites, per-child calendars with
save/duplicate/print, a token-gated read-only kiosk view for tablets,
and polling to keep parent and kiosk views in sync. Defaults to port 3007.

public/js/kiosk.js

@@ -0,0 +1,59 @@
+const token = window.location.pathname.split('/').filter(Boolean).pop();
+
+const weekdayBoard = document.getElementById('weekdayBoard');
+const weekendWrap = document.getElementById('weekendWrap');
+
+async function apiGet(path) {
+  const res = await fetch(path, { credentials: 'omit' });
+  if (!res.ok) throw new Error('request failed');
+  return res.json();
+}
+async function apiPatch(path, body) {
+  const res = await fetch(path, {
+    method: 'PATCH',
+    headers: { 'Content-Type': 'application/json' },
+    body: JSON.stringify(body),
+  });
+  if (!res.ok) throw new Error('request failed');
+  return res.json();
+}
+
+const handlers = {
+  onToggleDone: (taskId, done) => apiPatch(`/api/kiosk/${token}/tasks/${taskId}`, { done }).catch(() => {}),
+};
+
+function todayName() {
+  return new Date().toLocaleDateString('en-US', { weekday: 'long' });
+}
+
+function draw(calendar) {
+  document.getElementById('childName').textContent = calendar.childName || '';
+  document.getElementById('calTitle').textContent = calendar.title || '';
+
+  renderCalendar({
+    calendar,
+    editable: false,
+    weekdayBoard,
+    weekendWrap,
+    handlers,
+    todayName: todayName(),
+  });
+}
+
+async function poll() {
+  try {
+    const data = await apiGet(`/api/kiosk/${token}/calendar`);
+    if (!data.calendar) {
+      document.getElementById('emptyState').style.display = 'block';
+      document.getElementById('childName').textContent = data.child ? data.child.name : '';
+      return;
+    }
+    document.getElementById('emptyState').style.display = 'none';
+    draw(data.calendar);
+  } catch {
+    // transient network error — try again next tick
+  }
+}
+
+poll();
+setInterval(poll, 4000);