v0.6.2: show and manage on-phone sessions offline and signed out

A city-map timer started without signing in did not appear under Sessions.

The tab returned "Sign in to see your sessions" before rendering anything, so
a local session could never show; and even signed in it only ever listed
ParkSmarter's sessions. A local timer is the one kind that has no server copy,
which made it the one kind the screen could not display.

- Sessions now leads with "Tracking on this phone": the live countdown with
  +1 hour and End, working with no account and no network, because that is the
  only place the session exists.
- Recent local sessions are kept in a small on-device history (50 max). Without
  it a local session vanished the instant it ended — there is no server to ask.
  Paid ParkSmarter sessions are excluded so they don't appear twice.
- The ParkSmarter half is layered on top when signed in and can fail
  independently: offline it reports that and keeps the local half visible,
  rather than the whole tab going blank. It also no longer leaves an unhandled
  rejection when the fetch throws (it had try/finally but no catch).
- The card's second button follows the notification's rule: +1 hour for a local
  timer, Extend -> purchase screen for a bought session, since only one of those
  can honestly add time.

History is written in endActiveParking() before the record is dropped, which
also covers expiry — syncActiveParking() routes a lapsed session through the
same call.

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

app/app.json

@@ -3,14 +3,14 @@
     "name": "BigBrainParking",
     "slug": "bigbrainparking",
     "scheme": "bigbrainparking",
-    "version": "0.6.1",
+    "version": "0.6.2",
     "orientation": "portrait",
     "userInterfaceStyle": "automatic",
     "newArchEnabled": true,
     "icon": "./assets/icon.png",
     "android": {
       "package": "top.mowden.bigbrainparking",
-      "versionCode": 22,
+      "versionCode": 23,
       "edgeToEdgeEnabled": true,
       "adaptiveIcon": {
         "foregroundImage": "./assets/adaptive-icon.png",