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/calendar_screen.dart

@@ -235,8 +235,14 @@ class _CalendarRow extends StatelessWidget {
       leading: CircleAvatar(
         radius: 20,
         backgroundColor: swatch.fill,
-        foregroundImage:
-            entry.photo == null ? null : MemoryImage(entry.photo!),
+        // Decode to the 40px avatar size (× dpr), not the full photo.
+        foregroundImage: entry.photo == null
+            ? null
+            : ResizeImage(
+                MemoryImage(entry.photo!),
+                width: (40 * MediaQuery.devicePixelRatioOf(context)).round(),
+                height: (40 * MediaQuery.devicePixelRatioOf(context)).round(),
+              ),
         child: entry.photo == null
             ? Text(
                 entry.label.isEmpty