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.

test/api.test.js

@@ -26,6 +26,11 @@ test("API: до загрузки индекса сервер жив, но не
   assert.equal(health.body.ready, false);
   assert.equal(health.body.client, "127.0.0.1");
   assert.equal(typeof health.body.apiVersion, "number");
+  // Public health says alive, ready and versions; the rest is on the dashboard.
+  assert.equal(health.body.traffic, undefined);
+  assert.equal(health.body.telegram, undefined);
+  // Without DASHBOARD_PASSWORD the dashboard is off.
+  assert.equal((await get("/status/")).status, 404);
   const ready = await json("/api/ready");
   assert.equal(ready.status, 503);
   assert.equal(ready.body.code, "not_ready");