feat: implement dashboard with authentication and event logging

- Added dashboard functionality at /status with Basic Auth using DASHBOARD_PASSWORD.
- Created server-side event logging to track catalog and university status.
- Implemented traffic metrics tracking and display on the dashboard.
- Enhanced API tests to cover new dashboard features and authentication.
- Introduced CSS and JS for dashboard styling and functionality.
- Added tests for dashboard access control and data retrieval.

server/events.js

@@ -0,0 +1,39 @@
+import { readFile, writeFile, mkdir } from "node:fs/promises";
+import { DATA } from "./paths.js";
+
+// What happened to the catalog and the university, newest first, for the dashboard: the same
+// events the Telegram messages report, plus republished documents without new problems.
+// The last hundred are kept on disk, so a restart does not empty the feed.
+
+const FILE = "events.json";
+const MAX = 100;
+let events;
+
+async function load() {
+  if (events) return events;
+  try {
+    events = JSON.parse(await readFile(DATA + FILE, "utf8"));
+    if (!Array.isArray(events)) events = [];
+  } catch {
+    events = [];
+  }
+  return events;
+}
+
+/**
+ * Adds events: `{kind, title, text?, doc?}`. Kinds: new, republished, failed, year, year_late,
+ * source_down, source_up.
+ */
+export async function recordEvents(list) {
+  if (!list.length) return;
+  await load();
+  const t = new Date().toISOString();
+  events.unshift(...list.map((e) => ({ t, ...e })));
+  events.length = Math.min(events.length, MAX);
+  await mkdir(DATA, { recursive: true });
+  await writeFile(DATA + FILE, JSON.stringify(events));
+}
+
+export async function listEvents(limit = 50) {
+  return (await load()).slice(0, limit);
+}