feat: add secure login page with jwt authentication and button animation

src/App.tsx

@@ -1,16 +1,27 @@
-import { Routes, Route, Navigate } from 'react-router-dom';
+import { Routes, Route, Navigate, useLocation } from 'react-router-dom';
 import Layout from './components/Layout';
 import Dashboard from './pages/Dashboard';
 import Products from './pages/Products';
 import ProductDetails from './pages/ProductDetails';
 import Clients from './pages/Clients';
 import ClientDetails from './pages/ClientDetails';
+import Login from './pages/Login';
+import { isAuthenticated } from './dataService';
+
+function PrivateRoute({ children }: { children: JSX.Element }) {
+  const location = useLocation();
+  if (!isAuthenticated()) {
+    return <Navigate to="/login" state={{ from: location }} replace />;
+  }
+  return children;
+}
 
 function App() {
   return (
     <Routes>
+      <Route path="/login" element={<Login />} />
       <Route path="/" element={<Navigate to="/graph" replace />} />
-      <Route path="/" element={<Layout />}>
+      <Route path="/" element={<PrivateRoute><Layout /></PrivateRoute>}>
         <Route path="graph" element={<Dashboard />} />
         <Route path="products" element={<Products />} />
         <Route path="products/:id" element={<ProductDetails />} />