feat(auth): Implement LoginForm, RegisterForm and integrate with App

frontend/src/App.tsx

@@ -1,10 +1,56 @@
+import { useState, useEffect } from "react"
 import { MainLayout } from "./components/layout/MainLayout"
+import { LoginForm } from "./components/auth/LoginForm"
+import { RegisterForm } from "./components/auth/RegisterForm"
+import { AuthService } from "./services/auth"
 
 function App() {
+  const [isAuthenticated, setIsAuthenticated] = useState(false)
+  const [authMode, setAuthMode] = useState<"login" | "register">("login")
+
+  useEffect(() => {
+    setIsAuthenticated(AuthService.isAuthenticated())
+  }, [])
+
+  const handleAuthSuccess = () => {
+    setIsAuthenticated(true)
+  }
+
+  const handleLogout = () => {
+    AuthService.logout()
+    setIsAuthenticated(false)
+  }
+
+  if (!isAuthenticated) {
+    return (
+      <div className="min-h-screen flex items-center justify-center bg-background p-4">
+        {authMode === "login" ? (
+          <LoginForm
+            onSuccess={handleAuthSuccess}
+            onToggleMode={() => setAuthMode("register")}
+          />
+        ) : (
+          <RegisterForm
+            onSuccess={handleAuthSuccess}
+            onToggleMode={() => setAuthMode("login")}
+          />
+        )}
+      </div>
+    )
+  }
+
   return (
     <MainLayout>
       <div className="flex flex-col gap-4">
-        <h1 className="text-2xl font-bold">Welcome to Election Analytics</h1>
+        <div className="flex justify-between items-center">
+          <h1 className="text-2xl font-bold">Welcome to Election Analytics</h1>
+          <button
+            onClick={handleLogout}
+            className="text-sm text-muted-foreground hover:text-primary underline"
+          >
+            Logout
+          </button>
+        </div>
         <p className="text-muted-foreground">
           Select a conversation from the sidebar or start a new one to begin your analysis.
         </p>