fix: show toast and redirect on expired session (401)

Fix stale closure bug in QueryProvider (token ref) and add warning toast so users know why they were redirected to login.

k-tv-frontend/app/providers.tsx

@@ -7,8 +7,9 @@ import {
   MutationCache,
 } from "@tanstack/react-query";
 import { ReactQueryDevtools } from "@tanstack/react-query-devtools";
-import { useState } from "react";
+import { useState, useRef, useEffect } from "react";
 import { useRouter } from "next/navigation";
+import { toast } from "sonner";
 import { AuthProvider, useAuthContext } from "@/context/auth-context";
 import { Toaster } from "@/components/ui/sonner";
 import { ApiRequestError } from "@/lib/api";
@@ -16,6 +17,8 @@ import { ApiRequestError } from "@/lib/api";
 function QueryProvider({ children }: { children: React.ReactNode }) {
   const { token, setToken } = useAuthContext();
   const router = useRouter();
+  const tokenRef = useRef(token);
+  useEffect(() => { tokenRef.current = token; }, [token]);
 
   const [queryClient] = useState(() => {
     return new QueryClient({
@@ -23,7 +26,8 @@ function QueryProvider({ children }: { children: React.ReactNode }) {
         onError: (error) => {
           // Only redirect on 401 if the user had a token (expired session).
           // Guests hitting 401 on restricted content should not be redirected.
-          if (error instanceof ApiRequestError && error.status === 401 && token) {
+          if (error instanceof ApiRequestError && error.status === 401 && tokenRef.current) {
+            toast.warning("Session expired, please log in again.");
             setToken(null);
             router.push("/login");
           }
@@ -33,6 +37,7 @@ function QueryProvider({ children }: { children: React.ReactNode }) {
         onError: (error) => {
           // Mutations always require auth — redirect on 401 regardless.
           if (error instanceof ApiRequestError && error.status === 401) {
+            toast.warning("Session expired, please log in again.");
             setToken(null);
             router.push("/login");
           }