fix(client): 退单按钮改红色实心样式，与原型一致突出危险操作

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01YZ4DskSRKsSiheQonFtQvx

client/lib/widgets/order_row_actions.dart

@@ -35,16 +35,36 @@ List<Widget> buildOrderRowActions({
         onPressed: onPressed,
         child: Text(text, style: TextStyle(fontSize: 12, color: color)),
       );
+  // 实心强调按钮（用于「退单」这类需突出的危险操作，与原型一致）。
+  Widget filledBtn(String text, Color color, VoidCallback onPressed, {Key? key}) =>
+      Padding(
+        padding: const EdgeInsets.symmetric(horizontal: 4),
+        child: ElevatedButton(
+          key: key,
+          onPressed: onPressed,
+          style: ElevatedButton.styleFrom(
+            backgroundColor: color,
+            foregroundColor: Colors.white,
+            elevation: 0,
+            visualDensity: VisualDensity.compact,
+            tapTargetSize: MaterialTapTargetSize.shrinkWrap,
+            minimumSize: const Size(0, 30),
+            padding: const EdgeInsets.symmetric(horizontal: 12),
+            textStyle: const TextStyle(fontSize: 12, fontWeight: FontWeight.w500),
+          ),
+          child: Text(text),
+        ),
+      );
   return [
     btn('详情', AppTheme.primary, onDetail),
     btn('打印', AppTheme.primary, onPrint),
     ...afterPrint,
     if (!readonly && status == 'approved')
       WriteGuard(child: btn('结清', AppTheme.accent, onSettle)),
-    // 退单（已审核单退货）：error 样式，按权限显示
+    // 退单（已审核单退货）：红色实心按钮突出（与原型一致），按权限显示
     if (!readonly && status == 'approved' && canReturn)
       WriteGuard(
-          child: btn('退单', AppTheme.danger, onReturn,
+          child: filledBtn('退单', AppTheme.danger, onReturn,
               key: Key('btn_return_$orderId'))),
     if (!readonly && status == 'draft') ...[
       WriteGuard(child: btn('修改', AppTheme.primary, onEdit)),