feat: PresenceBar component shows who is watching each page

Made-with: Cursor

frontend/src/App.jsx

@@ -7,6 +7,7 @@ import Logo from './components/Logo';
 import ThemeToggle from './components/ThemeToggle';
 import InstallPrompt from './components/InstallPrompt';
 import SafariInstallPrompt from './components/SafariInstallPrompt';
+import PresenceBar from './components/PresenceBar';
 import Home from './pages/Home';
 import Login from './pages/Login';
 import Picker from './pages/Picker';
@@ -156,6 +157,9 @@ function App() {
         </div>
       </nav>
 
+      {/* Admin Presence */}
+      <PresenceBar />
+
       {/* Main Content */}
       <main className="container mx-auto px-4 py-8 flex-grow">
         <Routes>

frontend/src/components/PresenceBar.jsx

@@ -0,0 +1,41 @@
+import React from 'react';
+import { usePresence } from '../hooks/usePresence';
+import { useAuth } from '../context/AuthContext';
+
+function PresenceBar() {
+  const { isAuthenticated } = useAuth();
+  const { viewers } = usePresence();
+
+  if (!isAuthenticated) return null;
+
+  const otherViewers = viewers.filter(v => v !== 'me');
+  if (otherViewers.length === 0) return null;
+
+  return (
+    <div className="container mx-auto px-2 sm:px-4 pt-3">
+      <div className="bg-white dark:bg-gray-800 rounded-lg shadow-sm border border-gray-200 dark:border-gray-700 px-4 py-2">
+        <div className="flex items-center gap-3">
+          <span className="text-xs text-gray-500 dark:text-gray-400 uppercase tracking-wider font-medium flex-shrink-0">
+            who is watching
+          </span>
+          <div className="flex flex-wrap gap-1.5">
+            {viewers.map((name, i) => (
+              <span
+                key={`${name}-${i}`}
+                className={`inline-flex items-center px-2.5 py-0.5 rounded-full text-xs font-medium ${
+                  name === 'me'
+                    ? 'bg-indigo-100 dark:bg-indigo-900/40 text-indigo-700 dark:text-indigo-300'
+                    : 'bg-gray-100 dark:bg-gray-700 text-gray-700 dark:text-gray-300'
+                }`}
+              >
+                {name}
+              </span>
+            ))}
+          </div>
+        </div>
+      </div>
+    </div>
+  );
+}
+
+export default PresenceBar;