UX: notificaciones de chat con toast y sonido (WebAudio) + skeletons de carga en Agenda y Chat

frontend/src/App.tsx

@@ -4,6 +4,7 @@ import { ToastProvider } from './components/ui';
 import { AuthProvider, useAuth } from './lib/auth';
 import { QuickLinksProvider } from './lib/quicklinks';
 import { PatientDrawerProvider } from './components/PatientDrawer';
+import ChatNotifications from './lib/chat-notifications';
 import Dashboard from './pages/Dashboard';
 import Agenda from './pages/Agenda';
 import Pacientes from './pages/Pacientes';
@@ -63,6 +64,7 @@ const App: FC = () => {
         <Router>
         <ToastProvider />
         <PatientDrawerProvider>
+        <ChatNotifications />
         <Routes>
           <Route path="/login" element={<LoginRoute />} />
           <Route path="/" element={<RequireAuth href="/"><HomeRoute /></RequireAuth>} />