feat(story-1.5): add React frontend with auth pages and dark theme

web/src/App.tsx

@@ -0,0 +1,53 @@
+import { useEffect } from 'react';
+import { BrowserRouter, Routes, Route, Navigate } from 'react-router-dom';
+import { QueryClient, QueryClientProvider } from '@tanstack/react-query';
+import { useAuthStore } from './stores/authStore';
+import { authApi } from './api/auth';
+import { LoginPage } from './pages/LoginPage';
+import { RegisterPage } from './pages/RegisterPage';
+import { DashboardPage } from './pages/DashboardPage';
+import { ProtectedRoute } from './components/ProtectedRoute';
+import './App.css';
+
+const queryClient = new QueryClient({
+  defaultOptions: {
+    queries: {
+      retry: 1,
+      staleTime: 5 * 60 * 1000, // 5 minutes
+    },
+  },
+});
+
+function AuthChecker({ children }: { children: React.ReactNode }) {
+  const { setUser, setLoading } = useAuthStore();
+
+  useEffect(() => {
+    // Check if user is authenticated on app load
+    authApi.getMe()
+      .then((user) => setUser(user))
+      .catch(() => setUser(null));
+  }, [setUser, setLoading]);
+
+  return <>{children}</>;
+}
+
+function App() {
+  return (
+    <QueryClientProvider client={queryClient}>
+      <BrowserRouter>
+        <AuthChecker>
+          <Routes>
+            <Route path="/login" element={<LoginPage />} />
+            <Route path="/register" element={<RegisterPage />} />
+            <Route element={<ProtectedRoute />}>
+              <Route path="/" element={<DashboardPage />} />
+            </Route>
+            <Route path="*" element={<Navigate to="/" replace />} />
+          </Routes>
+        </AuthChecker>
+      </BrowserRouter>
+    </QueryClientProvider>
+  );
+}
+
+export default App;