v0.6.1: stop Anonymous Mode bouncing to sign-in on every foreground

Parking without an account showed "Your session expired — please sign in
again." repeatedly and kicked the user back to the login screen.

The 401 hook on the API client is global: it fires on every unauthorized
response whether or not the caller caught the error. Anonymous Mode has no
token, so any ParkSmarter call 401s, and two of them run automatically —
discoverPaidSession() on open and every foreground, and the map's
lastSessionLot() on every mount. Each one flipped the status to signedOut;
re-entering anonymous mode ran them again, hence "over and over".

Both call sites already caught their errors, which is why this hid: the
bounce came from the client hook, not from the catch.

- A 401 in Anonymous Mode is no longer treated as a session expiry. There is
  no session to expire, and bouncing to sign-in makes the mode pointless.
  This also covers the Sessions/Favorites/Scan tabs, which 401 the same way.
- authBus carries the mode to the non-React modules that need it.
- discoverPaidSession() and lastSessionLot() are skipped entirely when
  anonymous rather than fired and discarded.
- "Last lot" now says it needs an account instead of silently doing nothing.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

app/src/features/session/activeParking.ts

@@ -5,6 +5,7 @@ import type { NativeStackNavigationProp } from '@react-navigation/native-stack';
 import * as Notifications from 'expo-notifications';
 import type { Zone } from 'parksmarter-client';
 import { ps } from '@/api/client';
+import { authBus } from '@/auth/authBus';
 import { parseApiTime } from '@/api/parseTime';
 import type { LabelKind } from '@/api/zoneLabels';
 import type { RootStackParamList } from '@/navigation/RootNavigator';
@@ -326,8 +327,9 @@ export async function syncActiveParking(onExtend: (zone?: Zone) => void): Promis
   }
 
   // A city-map session is never on the ParkSmarter server, so don't let a stale
-  // server session overwrite it.
-  if (!current) current = await discoverPaidSession();
+  // server session overwrite it. In Anonymous Mode there is no account to ask at
+  // all — asking anyway would 401 on every single foreground.
+  if (!current && !authBus.isAnonymous) current = await discoverPaidSession();
 
   if (current) {
     await postNotification(current);