fix: prevent custom scale dialog from closing when interacting with slider

Wrapped MobileCustomScaleControls in GestureDetector with opaque behavior
to prevent touch events from propagating to parent dialog's clickMaskDismiss
handler. The slider now works correctly without closing the dialog.

Signed-off-by: Alessandro De Blasis <alex@deblasis.net>

flutter/lib/mobile/pages/remote_page.dart

@@ -25,6 +25,7 @@ import '../../models/model.dart';
 import '../../models/platform_model.dart';
 import '../../utils/image.dart';
 import '../widgets/dialog.dart';
+import '../widgets/custom_scale_widget.dart';
 
 final initText = '1' * 1024;
 
@@ -1201,6 +1202,14 @@ void showOptions(
                     if (v != null) viewStyle.value = v;
                   }
                 : null)),
+      // Show custom scale controls when custom view style is selected
+      Obx(() => viewStyle.value == kRemoteViewStyleCustom
+          ? GestureDetector(
+              behavior: HitTestBehavior.opaque,
+              onTap: () {}, // Absorb tap events to prevent dialog dismiss
+              child: MobileCustomScaleControls(ffi: gFFI),
+            )
+          : SizedBox.shrink()),
       const Divider(color: MyTheme.border),
       for (var e in imageQualityRadios)
         Obx(() => getRadio<String>(