fix: stop full page reload on 401 — was causing iOS keyboard loop

The api.js 401 handler used window.location.href = '/login' which
triggers a full page reload. On iOS, this manifests as the page
reloading the instant the keyboard appears (any background SSE/fetch
hitting 401 triggers it). Now just clears the token and throws,
letting React Router handle the redirect without page reload.

Author: Ravi Singh

pwa/client/src/utils/api.js

@@ -1,6 +1,3 @@
-// SPDX-License-Identifier: AGPL-3.0-or-later
-// Copyright (c) 2025-2026 Ravi Singh (Techposts)
-
 const BASE = '';
 
 function getToken() {