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/main.dart

@@ -1,3 +1,4 @@
+import 'package:flutter/services.dart';
 import 'package:flutter/widgets.dart';
 
 import 'bootstrap.dart';
@@ -6,6 +7,16 @@ import 'ui/restart_widget.dart';
 
 void main() {
   WidgetsFlutterBinding.ensureInitialized();
+  // Draw behind the system bars (edge-to-edge) with transparent bars, so the app
+  // fills the screen on Android 15+ (where edge-to-edge is enforced) and stays
+  // consistent elsewhere. Scaffolds use SafeArea to keep content off the insets.
+  SystemChrome.setEnabledSystemUIMode(SystemUiMode.edgeToEdge);
+  SystemChrome.setSystemUIOverlayStyle(
+    const SystemUiOverlayStyle(
+      statusBarColor: Color(0x00000000),
+      systemNavigationBarColor: Color(0x00000000),
+    ),
+  );
   // Start from the device language, then let an explicit in-app choice win —
   // it's the only reliable way to reach languages the OS picker doesn't offer
   // (e.g. Asturian). The saved choice is restored inside [Bootstrap], after DI.