Add streaks, today view, custom plan editing/chapter ranges, and ntfy reminders

Reading plans now track a cross-plan activity log for streaks, surface a
combined "today's reading" view on both Home and the Reading Plans page,
and let custom plans be edited after creation (including narrowing a book
to a specific chapter range). The reader auto-marks a plan's day read after
a dwell period, active plans that fall behind their pace get a "catch me
up" banner, and a new Settings section wires up daily reading reminders
via ntfy.sh, checked once a minute by a small server-side scheduler.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

server/reminders.js

@@ -0,0 +1,52 @@
+// Daily "don't forget to read" reminders, sent via ntfy.sh (https://ntfy.sh) —
+// a free pub/sub push service: POST a message to a topic URL, anyone
+// subscribed to that topic (via the ntfy app or a browser) gets notified.
+// No API keys or push-subscription plumbing needed.
+import { getUsersWithRemindersEnabled, setLastReminderDate, getReadingProgress } from './db.js';
+
+function todayDateString(d = new Date()) {
+  return `${d.getFullYear()}-${String(d.getMonth() + 1).padStart(2, '0')}-${String(d.getDate()).padStart(2, '0')}`;
+}
+
+function currentHHMM(d = new Date()) {
+  return `${String(d.getHours()).padStart(2, '0')}:${String(d.getMinutes()).padStart(2, '0')}`;
+}
+
+async function sendNtfyReminder(user) {
+  const base = (user.ntfyUrl || 'https://ntfy.sh').replace(/\/+$/, '');
+  const url = `${base}/${encodeURIComponent(user.ntfyTopic)}`;
+  const res = await fetch(url, {
+    method: 'POST',
+    headers: { Title: 'Reading Plan Reminder', Tags: 'open_book' },
+    body: "Don't forget today's reading!",
+  });
+  if (!res.ok) throw new Error(`ntfy responded ${res.status}`);
+}
+
+async function checkReminders() {
+  const now = new Date();
+  const hhmm = currentHHMM(now);
+  const today = todayDateString(now);
+  const due = getUsersWithRemindersEnabled().filter(
+    (u) => u.reminderTime === hhmm && u.lastReminderDate !== today,
+  );
+
+  for (const user of due) {
+    try {
+      const progress = getReadingProgress(user.id);
+      const hasActivePlan = Array.isArray(progress?.progress) && progress.progress.some((p) => !p.completedAt);
+      if (!hasActivePlan) continue; // nothing to nudge them about
+      await sendNtfyReminder(user);
+      setLastReminderDate(user.id, today);
+    } catch (err) {
+      console.error(`Reading reminder failed for user ${user.id}:`, err.message);
+    }
+  }
+}
+
+/** Checks once a minute whether any user's reminder time has arrived. */
+export function startReminderScheduler() {
+  setInterval(() => {
+    checkReminders().catch((err) => console.error('Reminder scheduler error:', err));
+  }, 60 * 1000);
+}