fix(frontend): copilot redirect logout (#12050)

## Changes 🏗️

Redirect to `/login` if the user is not authenticated and tries to
access `/copilot`

### Checklist 📋

#### For code changes:
- [x] I have clearly listed my changes in the PR description
- [x] I have made a test plan
- [x] I have tested my changes according to the test plan:
  - [x] Run the app locally and tested

autogpt_platform/frontend/src/app/(platform)/copilot/useCopilotPage.ts

@@ -3,6 +3,7 @@ import { useBreakpoint } from "@/lib/hooks/useBreakpoint";
 import { useSupabase } from "@/lib/supabase/hooks/useSupabase";
 import { useChat } from "@ai-sdk/react";
 import { DefaultChatTransport } from "ai";
+import { useRouter } from "next/navigation";
 import { useEffect, useMemo, useState } from "react";
 import { useChatSession } from "./useChatSession";
 
@@ -10,6 +11,7 @@ export function useCopilotPage() {
   const { isUserLoading, isLoggedIn } = useSupabase();
   const [isDrawerOpen, setIsDrawerOpen] = useState(false);
   const [pendingMessage, setPendingMessage] = useState<string | null>(null);
+  const router = useRouter();
 
   const {
     sessionId,
@@ -52,6 +54,10 @@ export function useCopilotPage() {
     transport: transport ?? undefined,
   });
 
+  useEffect(() => {
+    if (!isUserLoading && !isLoggedIn) router.replace("/login");
+  }, [isUserLoading, isLoggedIn]);
+
   useEffect(() => {
     if (!hydratedMessages || hydratedMessages.length === 0) return;
     setMessages((prev) => {