feat(auth): use the cookie session and refresh on 401

The token is no longer stored; a tbp_session flag remembers the
login. apiFetch renews the session once on a 401 and sends the
request again. Parallel requests and other tabs share one refresh,
because Auth revokes the session when a refresh token is used twice.
Only a 401 from the refresh ends the session; a 502 or no network
shows the normal error.

src/pages/PlayNextPage.jsx

@@ -14,7 +14,7 @@ import useSessionExpired from '../hooks/useSessionExpired.js';
 import {saveGameStatus} from '../utils/backlog.js';
 import {formatPlaytime} from '../utils/games.js';
 import {apiFetch} from '../utils/api.js';
-import {getToken} from '../utils/auth.js';
+import {hasSession} from '../utils/auth.js';
 
 // maxMinutes is IGDB's normal time to beat; a limit leaves out games without IGDB data.
 const BUDGETS = [
@@ -47,7 +47,7 @@ export default function PlayNextPage() {
     const latestRequest = useRef(0);
 
     const load = useCallback(async (maxMinutes, exclude) => {
-        if (!getToken()) {
+        if (!hasSession()) {
             navigate('/login');
             return;
         }