App 2.16.1: Overview values every half second

The Overview read the car every 2 s, on the main thread. It now reads
every 0.5 s on a background thread (one reader; a read still running
makes the next tick skip rather than queue) and shows the values on the
main thread. The consumption and charging trackers stay on the 2-second
tick with the newest reading: they integrate over time, and the
charging tracker writes its session to storage on every sample.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01QLJfZQZeAKAwSqViTmLzki

SPECS.md

@@ -109,6 +109,11 @@ tyre pressures, GPS (lat, lon, elevation, heading) and the is_* flags. It does *
   INGEST_TOKEN) into git and pushed it. Commit amended and force-pushed; both values regenerated in
   the now gitignored `k8s/secrets.yaml` (since moved to `k8s/secrets/secrets.yaml`, outside
   `kubectl apply -f k8s/`). Filled-in secrets live only there from now on.
+- 2026-10-18 — App 2.16.1: the Overview reads the car every 0.5 s (was 2 s), on a background
+  thread; the consumption and charging trackers stay on the 2-second tick (they integrate over
+  time, and the charging tracker writes its session to storage on every sample). Note for
+  emulator tests: uiautomator can no longer dump the screen while the Overview is open, since
+  the UI is never idle.
 - 2026-10-18 — Grafana's read-only InfluxDB token without a manual step: an init container in
   the Grafana pod creates it with the admin token at every start, deletes the previous one and
   leaves only the read-only token in a memory volume; the datasource reads it with