v0.2.2: active-session "time left" status notification (default on)

Starting a session posts an ongoing notification showing the expiry time + time
remaining, so you can glance at how long you have left without opening the app.
- Default ON; toggle in Account -> Notifications ("Active-session countdown").
- Kept fresh on app open / foreground (re-posts nearest-expiring active session,
  clears when none remain). Quiet channel, no banner/sound on refresh.
- Purely local (expo-notifications); no server/push.

Note: expo-notifications can't render a live per-second ticking countdown in the
background, so it shows the exact expiry time (always accurate) + remaining, and
refreshes on foreground. A true ticking chronometer would need notifee (native).

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

app/app.json

@@ -3,14 +3,14 @@
     "name": "BigBrainParking",
     "slug": "bigbrainparking",
     "scheme": "bigbrainparking",
-    "version": "0.2.1",
+    "version": "0.2.2",
     "orientation": "portrait",
     "userInterfaceStyle": "automatic",
     "newArchEnabled": true,
     "icon": "./assets/icon.png",
     "android": {
       "package": "top.mowden.bigbrainparking",
-      "versionCode": 11,
+      "versionCode": 12,
       "edgeToEdgeEnabled": true,
       "adaptiveIcon": {
         "foregroundImage": "./assets/adaptive-icon.png",