Fix Docker build error; add multi-year view, PDF export, ntfy notifier

Fix: remove unused 'accessibleMonths' variable (tsc exit code 2)

Features:
- AllYearsLetter view: all years in chronological order, reachable
  from "All Years" at the top of the sidebar
- PDF export: window.print() with @media print CSS — sidebar, toolbar,
  and chrome hidden; each year starts on a new page via page-break
- "Download all" exports a plain-text file of every year's letter
- ntfy notifier: standalone Node.js service (notifier/) that fires a
  push notification via ntfy on the 1st of each month; configurable
  via NTFY_TOPIC, NTFY_URL, CRON_SCHEDULE, APP_URL env vars
- docker-compose: adds `notifier` service alongside `app`; reads from
  .env (example in .env.example); NTFY_TEST_ON_START=true sends a
  test ping on container start

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

notifier/Dockerfile

@@ -0,0 +1,6 @@
+FROM node:20-alpine
+WORKDIR /app
+COPY package.json ./
+RUN npm install --omit=dev
+COPY index.mjs ./
+CMD ["node", "index.mjs"]

notifier/index.mjs

@@ -0,0 +1,63 @@
+import cron from "node-cron";
+
+const NTFY_URL = process.env.NTFY_URL || "https://ntfy.sh";
+const NTFY_TOPIC = process.env.NTFY_TOPIC;
+const CRON_SCHEDULE = process.env.CRON_SCHEDULE || "0 9 1 * *"; // 9 AM on the 1st of each month
+const APP_URL = process.env.APP_URL || "http://localhost:8080";
+
+if (!NTFY_TOPIC) {
+  console.error("NTFY_TOPIC is required. Set it in your environment or docker-compose.");
+  process.exit(1);
+}
+
+const MONTH_NAMES = [
+  "January", "February", "March", "April", "May", "June",
+  "July", "August", "September", "October", "November", "December",
+];
+
+async function sendReminder() {
+  const now = new Date();
+  // We fire on the 1st — remind for the month that just ended
+  const prevMonth = new Date(now.getFullYear(), now.getMonth() - 1, 1);
+  const monthName = MONTH_NAMES[prevMonth.getMonth()];
+  const year = prevMonth.getFullYear();
+
+  const title = `Time to write your ${monthName} letter`;
+  const message = `${monthName} ${year} is done. Take 10 minutes to capture the month before it fades. Open your letter app to answer this month's 6 prompts.`;
+
+  try {
+    const res = await fetch(`${NTFY_URL}/${NTFY_TOPIC}`, {
+      method: "POST",
+      headers: {
+        Title: title,
+        Priority: "default",
+        Tags: "pencil,calendar",
+        Click: APP_URL,
+        "Content-Type": "text/plain",
+      },
+      body: message,
+    });
+
+    if (res.ok) {
+      console.log(`[${new Date().toISOString()}] Reminder sent for ${monthName} ${year}`);
+    } else {
+      console.error(`[${new Date().toISOString()}] ntfy returned ${res.status}: ${await res.text()}`);
+    }
+  } catch (err) {
+    console.error(`[${new Date().toISOString()}] Failed to send reminder:`, err.message);
+  }
+}
+
+console.log(`[${new Date().toISOString()}] Notifier started`);
+console.log(`  Topic:    ${NTFY_URL}/${NTFY_TOPIC}`);
+console.log(`  Schedule: ${CRON_SCHEDULE}`);
+console.log(`  App URL:  ${APP_URL}`);
+
+// Run on schedule
+cron.schedule(CRON_SCHEDULE, sendReminder, { timezone: "America/Chicago" });
+
+// Send a startup test ping in dev mode
+if (process.env.NTFY_TEST_ON_START === "true") {
+  console.log("Sending test notification on startup...");
+  sendReminder();
+}

notifier/package.json

@@ -0,0 +1,9 @@
+{
+  "name": "letter-notifier",
+  "version": "1.0.0",
+  "type": "module",
+  "main": "index.mjs",
+  "dependencies": {
+    "node-cron": "^3.0.3"
+  }
+}