feat: initial SPA frontend for network app

src/App.tsx

@@ -0,0 +1,49 @@
+import { useEffect } from 'react';
+import { BrowserRouter, Routes, Route, Navigate } from 'react-router-dom';
+import { useAuthStore } from '@/stores/auth';
+import Layout from '@/components/Layout';
+import LoginPage from '@/pages/LoginPage';
+import DashboardPage from '@/pages/DashboardPage';
+import ClientsPage from '@/pages/ClientsPage';
+import ClientDetailPage from '@/pages/ClientDetailPage';
+import EventsPage from '@/pages/EventsPage';
+import EmailsPage from '@/pages/EmailsPage';
+import SettingsPage from '@/pages/SettingsPage';
+import { PageLoader } from '@/components/LoadingSpinner';
+
+function ProtectedRoute({ children }: { children: React.ReactNode }) {
+  const { isAuthenticated, isLoading } = useAuthStore();
+  if (isLoading) return <PageLoader />;
+  if (!isAuthenticated) return <Navigate to="/login" replace />;
+  return <>{children}</>;
+}
+
+export default function App() {
+  const { checkSession, isAuthenticated } = useAuthStore();
+
+  useEffect(() => {
+    checkSession();
+  }, [checkSession]);
+
+  return (
+    <BrowserRouter>
+      <Routes>
+        <Route path="/login" element={
+          isAuthenticated ? <Navigate to="/" replace /> : <LoginPage />
+        } />
+        <Route path="/" element={
+          <ProtectedRoute>
+            <Layout />
+          </ProtectedRoute>
+        }>
+          <Route index element={<DashboardPage />} />
+          <Route path="clients" element={<ClientsPage />} />
+          <Route path="clients/:id" element={<ClientDetailPage />} />
+          <Route path="events" element={<EventsPage />} />
+          <Route path="emails" element={<EmailsPage />} />
+          <Route path="settings" element={<SettingsPage />} />
+        </Route>
+      </Routes>
+    </BrowserRouter>
+  );
+}