perf(android): R8, bitmap downscaling, edge-to-edge; recover device compat; publish to production

Device compatibility (regression fix):
- The CAMERA permission (from zxing_barcode_scanner / image_picker) implicitly
  required android.hardware.camera, excluding camera-less devices — Play showed
  Automotive -96%, Chromebook -86%, TV -25%. Declare camera & location
  uses-feature required="false" to keep those devices supported.
- Detect a real camera at runtime (PackageManager.FEATURE_CAMERA_ANY via the
  existing MethodChannel), cache it at bootstrap, and hide the QR scan button and
  the camera photo-source option when absent, so no broken actions are offered.

Play "app optimization" recommendations:
- Enable R8 (isMinifyEnabled + isShrinkResources) with keep rules for the
  OCR (tesseract4android), SQLCipher and notifications JNI/reflection code.
- Bitmap downscaling: cacheWidth/cacheHeight (and ResizeImage for avatars) on
  list thumbnails and avatars so photos decode to on-screen size, not full res.
- Edge-to-edge: opt in with transparent system bars in main().

Release flow:
- Tagged builds now publish to the production track at 100% (was internal);
  add a manual deploy_internal lane as a QA safety net.
- Document country/region availability as a Play Console setting (not in-repo).

apps/app_seeds/lib/bootstrap.dart

@@ -9,6 +9,7 @@ import 'data/variety_repository.dart';
 import 'di/injector.dart';
 import 'i18n/strings.g.dart';
 import 'services/auto_backup_service.dart';
+import 'services/camera_availability.dart';
 import 'services/coarse_location.dart';
 import 'services/inbox_service.dart';
 import 'services/locale_store.dart';
@@ -50,6 +51,11 @@ class _BootstrapState extends State<Bootstrap> {
   Future<TaneApp> _boot() async {
     await configureDependencies();
 
+    // Detect camera presence once, before the home screen builds, so camera-less
+    // devices (Chromebooks, Automotive, some TVs) hide the QR scan / camera UI
+    // instead of offering broken actions. Non-Android platforms keep the default.
+    await initCameraAvailability();
+
     // The saved language lives in the keystore, so it can only be applied once
     // DI is up. Until now the splash showed in the device language (it has no
     // text), so there is no visible flip.