Restore web identity photo previews (#69)

frontend/app/lib/kyc/preview.dart

@@ -1,3 +1,5 @@
+import 'dart:typed_data';
+
 import 'package:flutter/material.dart';
 
 import 'package:sxchnge_kyc/sxchnge_kyc.dart';
@@ -15,8 +17,12 @@ class PhotoPreview extends StatefulWidget {
 
 class _PhotoPreviewState extends State<PhotoPreview> {
   late ImageProvider _image = _provider();
-  ImageProvider _provider() =>
-      ResizeImage.resizeIfNeeded(1000, null, MemoryImage(widget.photo.bytes));
+  ImageProvider _provider() => ResizeImage.resizeIfNeeded(
+    1000,
+    null,
+    // Web decoders require a native typed array, not the model's read-only view.
+    MemoryImage(Uint8List.fromList(widget.photo.bytes)),
+  );
   @override
   void didUpdateWidget(covariant PhotoPreview oldWidget) {
     super.didUpdateWidget(oldWidget);
@@ -38,7 +44,15 @@ class _PhotoPreviewState extends State<PhotoPreview> {
     height: 220,
     fit: BoxFit.contain,
     semanticLabel: widget.label,
-    errorBuilder: (_, _, _) =>
-        Text(AppLocalizations.of(context)!.kycErrorUnreadable),
+    errorBuilder: (_, _, _) => ConstrainedBox(
+      constraints: const BoxConstraints(minHeight: 220),
+      child: Center(
+        child: Semantics(
+          container: true,
+          liveRegion: true,
+          child: Text(AppLocalizations.of(context)!.kycErrorPreview),
+        ),
+      ),
+    ),
   );
 }