test(frontend): add vitest test suite and apply code formatting

frontend/public/admin/users.html

@@ -1,24 +1,24 @@
 <div class="panel-header-row">
-    <div>
-        <h1>Users</h1>
-        <p>Current room presence derived from Redis presence keys.</p>
-    </div>
-    <button id="reload-users-btn" type="button" class="btn btn-secondary">Reload users</button>
+  <div>
+    <h1>Users</h1>
+    <p>Current room presence derived from Redis presence keys.</p>
+  </div>
+  <button id="reload-users-btn" type="button" class="btn btn-secondary">Reload users</button>
 </div>
 
 <div class="panel-card">
-    <div class="table-wrap">
-        <table class="data-table">
-            <thead>
-                <tr>
-                    <th>Username</th>
-                    <th>Room</th>
-                    <th>Online</th>
-                    <th>Actions</th>
-                </tr>
-            </thead>
-            <tbody id="users-table-body"></tbody>
-        </table>
-    </div>
-    <p id="users-status" class="status-line" aria-live="polite">Loading active users...</p>
-</div>
+  <div class="table-wrap">
+    <table class="data-table">
+      <thead>
+        <tr>
+          <th>Username</th>
+          <th>Room</th>
+          <th>Online</th>
+          <th>Actions</th>
+        </tr>
+      </thead>
+      <tbody id="users-table-body"></tbody>
+    </table>
+  </div>
+  <p id="users-status" class="status-line" aria-live="polite">Loading active users...</p>
+</div>