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/watch.test.js

@@ -7,7 +7,8 @@ import { startApi, fixture } from "./support/nextcloud.js";
 // rebuilt only for a changed document, and messages to the owner in Telegram (a stand-in here).
 let api, telegram, watch;
 const messages = [];
-const health = async () => (await fetch(api.base + "/api/health")).json();
+// What the dashboard shows (/status, behind its password).
+const health = async () => (await fetch(api.base + "/status/data.json", { headers: { Authorization: "Basic " + Buffer.from("admin:secret").toString("base64") } })).json();
 const lastMessage = () => messages.at(-1)?.text || "";
 
 before(async () => {
@@ -29,6 +30,7 @@ before(async () => {
     PSU_ALERT_SOURCE_DOWN_MS: "0",
     // Every check reaches the stand-in, however soon after the last one.
     PSU_MIN_REFRESH_MS: "0",
+    DASHBOARD_PASSWORD: "secret",
   });
   watch = await import("../server/watch.js");
 });
@@ -109,5 +111,13 @@ test("Наблюдение: университет не отвечает и сн
   await watch.watchOnce();
   assert.equal(messages.length, 5);
   assert.match(lastMessage(), /снова отвечает/);
-  assert.equal((await health()).watch.lastError, null);
+  const { watch: after, events } = await health();
+  assert.equal(after.lastError, null);
+  // The dashboard's feed, newest first: everything above, republished-as-is included.
+  assert.deepEqual(
+    events.map((e) => e.kind),
+    ["source_up", "source_down", "republished", "republished", "new"],
+  );
+  assert.equal(events[2].text, "без новых подозрительных ячеек");
+  assert.match(events[3].text, /новых подозрительных ячеек: 1/);
 });