feat(auth): refresh tokens + remember me

Backend: add refresh JWT (30d, token_type claim), POST /auth/refresh
endpoint (rotates token pair), remember_me on login, JWT_REFRESH_EXPIRY_DAYS
env var. Extractors now reject refresh tokens on protected routes.

Frontend: sessionStorage for non-remembered sessions, localStorage +
refresh token for remembered sessions. Transparent 401 recovery in
api.ts (retry once after refresh). Remember me checkbox on login page
with security note when checked.

k-tv-frontend/app/providers.tsx

@@ -15,7 +15,7 @@ import { Toaster } from "@/components/ui/sonner";
 import { ApiRequestError } from "@/lib/api";
 
 function QueryProvider({ children }: { children: React.ReactNode }) {
-  const { token, setToken } = useAuthContext();
+  const { token, setTokens } = useAuthContext();
   const router = useRouter();
   const tokenRef = useRef(token);
   useEffect(() => { tokenRef.current = token; }, [token]);
@@ -29,7 +29,7 @@ function QueryProvider({ children }: { children: React.ReactNode }) {
           // Guests hitting 401 on restricted content should not be redirected.
           if (error instanceof ApiRequestError && error.status === 401 && tokenRef.current) {
             toast.warning("Session expired, please log in again.");
-            setToken(null);
+            setTokens(null, null, false);
             router.push("/login");
           }
         },
@@ -39,7 +39,7 @@ function QueryProvider({ children }: { children: React.ReactNode }) {
           // 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);
+            setTokens(null, null, false);
             router.push("/login");
           }
         },