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

app/build.gradle

@@ -34,8 +34,8 @@ android {
         applicationId "com.stinnesbeck.nilsmg4"
         minSdk 27
         targetSdk 36
-        versionCode 84
-        versionName "2.16.0"
+        versionCode 85
+        versionName "2.16.1"
 
         // Nothing about the server ships in the APK: its URL and ingest token are entered in
         // the app's Server tab (ServerConfig), and the database is only reachable by the server.