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/app.json

@@ -44,6 +44,7 @@
     ],
     "extra": {
       "psEnvironment": "prodv2",
+      "zoneLabelsApiUrl": "https://bigbrainparking.mowden.top",
       "mapStyleUrl": "https://tiles.openfreemap.org/styles/liberty",
       "mapStyleUrlDark": "https://basemaps.cartocdn.com/gl/dark-matter-gl-style/style.json",
       "unifiedPushDefaultDistributor": "io.heckel.ntfy",