feat(auth): implement WebSocket authentication for admin access to logs

frontend/README.md

@@ -58,5 +58,5 @@ frontend/
 
 ## Caveats
 
-- The backend's `/api/system/getLogs` websocket is currently unauthenticated — anyone who can reach the port can read logs. Consider gating it in a future backend change.
+- The log websocket needs an `admin` token, and a browser cannot set headers on a WebSocket handshake, so the token rides in the query string (`/api/system/getLogs?token=…&timestamp=…`). That URL is a credential: it can end up in proxy and access logs, so don't paste it into third-party tools. The view reconnects with a fresh token from `localStorage` on every attempt.
 - Registering more than one user is intentionally impossible; the backend only accepts the very first registration.

frontend/src/views/Logs.vue

@@ -1,5 +1,6 @@
 <script setup>
 import { computed, onBeforeUnmount, onMounted, reactive, ref } from 'vue';
+import { getToken } from '../utils/auth.js';
 import { LOG_LEVELS } from '../utils/fmt.js';
 
 const MAX_LOGS = 1200;
@@ -38,7 +39,14 @@ const statusText = computed(() => {
 
 function wsUrl() {
     const proto = window.location.protocol === 'https:' ? 'wss:' : 'ws:';
-    return `${proto}//${window.location.host}/api/system/getLogs`;
+    // The backend only upgrades the request for an admin token. A browser cannot
+    // set headers on a WebSocket handshake, so the credentials travel in the
+    // query string — the URL itself is therefore a secret.
+    const params = new URLSearchParams({
+        token: getToken(),
+        timestamp: String(Math.floor(Date.now() / 1000))
+    });
+    return `${proto}//${window.location.host}/api/system/getLogs?${params}`;
 }
 
 function connect() {
@@ -49,6 +57,11 @@ function connect() {
     if (ws) {
         try { ws.close(); } catch { /* ignore */ }
     }
+    // Signed out: the handshake would be rejected, so don't spin on reconnects.
+    if (!getToken()) {
+        status.value = 'closed';
+        return;
+    }
     status.value = 'connecting';
 
     try {