fix(ui): improve cross-platform text input behavior (#1477)

ui/flutter/lib/features/tasks/presentation/widgets/task_drawer.dart

@@ -9,6 +9,7 @@ import 'package:shadcn_flutter/shadcn_flutter.dart' as shad;
 import '../../../../shared/theme/app_design_tokens.dart';
 import '../../../../shared/theme/app_palette.dart';
 import '../../../../shared/widgets/app_copy_icon_button.dart';
+import '../../../../shared/widgets/app_text_field.dart';
 import '../../../../shared/widgets/app_tooltip.dart';
 import '../../../../shared/widgets/detail/app_detail_surface.dart';
 import '../../../../core/utils/text_wrap.dart';
@@ -512,7 +513,7 @@ class _EditableUrlBlock extends StatelessWidget {
               children: [
                 SizedBox(
                   height: 76,
-                  child: shad.TextField(
+                  child: AppTextField(
                     controller: controller,
                     minLines: null,
                     maxLines: null,

ui/flutter/lib/features/tasks/presentation/widgets/task_update_url_dialog.dart

@@ -4,6 +4,7 @@ import 'package:shadcn_flutter/shadcn_flutter.dart' hide Column, Expanded, Row;
 import '../../../../shared/theme/app_palette.dart';
 import '../../../../shared/widgets/app_http_headers_editor.dart';
 import '../../../../shared/widgets/app_primary_button.dart';
+import '../../../../shared/widgets/app_text_field.dart';
 import '../../../../l10n/l10n.dart';
 import '../../domain/task_record.dart';
 
@@ -47,7 +48,7 @@ Future<TaskUrlUpdate?> showTaskUpdateUrlDialog(BuildContext context, TaskRecord
                   children: [
                     Text(dialogContext.l10n.downloadLink, style: TextStyle(color: palette.textPrimary, fontSize: 12)),
                     const SizedBox(height: 6),
-                    TextField(controller: urlController),
+                    AppTextField(controller: urlController),
                     const SizedBox(height: 18),
                     AppHttpHeadersEditor(
                       controller: headersController,