app: zone-labels client + admin labeling UX (Phase B) + default map = downtown Sandpoint

- zoneLabels client (cached fetch wrapper) hitting bigbrainparking.mowden.top;
  adminStore keeps the admin password in secure-store.
- Admin screen (verify + save password) reachable from Account → Admin.
- MeterDetail shows a label badge and, for admins, 2h/3h/4h/Pay-now/Clear
  labeling controls that PUT/DELETE to the API.
- app.json extra.zoneLabelsApiUrl.
- Map default view is now downtown Sandpoint (48.2766,-116.5533 @ z14) instead
  of the continental-US fallback.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

app/src/screens/MapScreen.tsx

@@ -24,9 +24,9 @@ const MAP_STYLE_DARK =
   (Constants.expoConfig?.extra?.mapStyleUrlDark as string) ??
   'https://basemaps.cartocdn.com/gl/dark-matter-gl-style/style.json';
 
-// Fallback view when we have no GPS and no cached location (continental US).
-const DEFAULT_CENTER: Coords = { latitude: 39.5, longitude: -98.35 };
-const DEFAULT_ZOOM = 4;
+// Default view when we have no last-session lot: all of downtown Sandpoint, ID.
+const DEFAULT_CENTER: Coords = { latitude: 48.2766, longitude: -116.5533 };
+const DEFAULT_ZOOM = 14;
 
 type Nav = NativeStackNavigationProp<RootStackParamList>;