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/components/BacklogCard.jsx

@@ -13,7 +13,7 @@ import {cn} from '@/lib/utils';
 import {STATUS_META} from './GameStatusBadge.jsx';
 import {GAME_PRIORITIES, GAME_STATUSES, NO_PRIORITY, saveBacklogEntry, toBacklogRequest} from '../utils/backlog.js';
 import useSessionExpired from '../hooks/useSessionExpired.js';
-import {getToken} from '../utils/auth.js';
+import {hasSession} from '../utils/auth.js';
 
 const NOTES_MAX = 2000;
 
@@ -42,7 +42,7 @@ export default function BacklogCard({game, onSaved}) {
     const set = (field) => (value) => setForm((f) => ({...f, [field]: value}));
 
     const save = async () => {
-        if (!getToken()) {
+        if (!hasSession()) {
             navigate('/login');
             return;
         }