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/ui/qr_scan.dart

@@ -7,12 +7,17 @@ import 'package:zxing_barcode_scanner/zxing_barcode_scanner.dart';
 import '../data/species_repository.dart';
 import '../data/variety_repository.dart';
 import '../i18n/strings.g.dart';
+import '../services/camera_availability.dart';
 import '../services/seed_label_scan.dart';
 
 /// Whether this platform can open the camera scanner. Mobile-only for now
 /// (pure-ZXing platform views; no Google Play Services) — elsewhere the scan
-/// button simply isn't offered, same pattern as the OCR capture.
-bool get qrScanSupported => !kIsWeb && (Platform.isAndroid || Platform.isIOS);
+/// button simply isn't offered, same pattern as the OCR capture. On Android it
+/// also requires an actual camera, so camera-less devices (Chromebooks,
+/// Automotive, some TVs) don't get a scan button that can't open — see
+/// [deviceHasCamera].
+bool get qrScanSupported =>
+    !kIsWeb && ((Platform.isAndroid && deviceHasCamera) || Platform.isIOS);
 
 /// Opens the full-screen camera scanner and returns the first decoded QR
 /// payload, or null if the person backed out. (Ğ1nkgo's scanner pattern on