feat(android): release signing + R8-verified signed APK (Phase 28.8)

PLAN.md

@@ -2229,14 +2229,13 @@ The app reuses the existing Pi REST API surface with no changes:
   dark top bar.
 - Follow-up polish deferred: card shadows, blue `btn-primary` buttons, page titles.
 
-**28.8 — Polish + distribution**
-- App icon, splash screen, dark theme polish
-- Error handling: Pi unreachable, server unreachable, no cellular data, storage full
-- APK signing + release build
-- Distribution: APK sideload (simplest — host the APK on the Pi itself at
-  `http://yaris.local/app/yaris-obd.apk` so the user just opens that URL on the phone
-  to install/update). Play Store is out of scope (Google developer account fee, review
-  process, updates lag behind development).
+**28.8 — Polish + distribution 🚧 IN PROGRESS (2026-08-15)**
+- ✅ App icon (adaptive, red bg + white gauge), native splash screen (API 31+), "Yaris OBD"
+  label, OS-following dark mode.
+- ✅ Release build: local signing keystore (gitignored), R8-verified — `app-release.apk`
+  (~43 MB) installs and launches on the Pixel.
+- ⬜ Distribution: host the APK on the Pi (`GET /app` → `static/app/` + download page).
+  Play Store out of scope.
 
 #### Open questions (resolve during 28.1)