App 2.15.0: queued live data survives restarts

Unsent live samples were kept in memory only, so a reboot or a killed
process during a dead spot lost them. The queue is now saved to
files/telemetry_queue.json with AtomicFile, at most every 5 minutes and
only after a change (the flash is not written every 15 s), and at once
when the service stops; it is restored, oldest first and within the
2000-sample cap, when the service starts. A damaged file restores
nothing rather than failing. Tested on the emulator across a reboot.

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 82
-        versionName "2.14.4"
+        versionCode 83
+        versionName "2.15.0"
 
         // 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.