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/metrics.js

@@ -185,8 +185,23 @@ export function trafficStatus(now = Date.now()) {
     for (const [client, n] of b.clients) hour.clients.set(client, (hour.clients.get(client) || 0) + n);
   }
   const busiest = [...hour.clients.entries()].sort((a, z) => z[1] - a[1]).slice(0, 3);
+  // Minute by minute, oldest first, empty minutes included: the dashboard's chart.
+  const current = Math.floor(now / 60000);
+  const series = Array.from({ length: WINDOW_MINUTES }, (_, i) => {
+    const minute = current - WINDOW_MINUTES + 1 + i;
+    const b = minutes.get(minute);
+    return {
+      t: new Date(minute * 60000).toISOString(),
+      requests: b?.requests || 0,
+      notModified: b?.notModified || 0,
+      errors: (b?.clientErrors || 0) + (b?.serverErrors || 0),
+      serverErrors: b?.serverErrors || 0,
+      slow: b?.slow || 0,
+    };
+  });
   return {
     since: started,
+    series,
     lastHour: {
       ...summary(hour),
       clients: hour.clients.size,