NSearchableCombobox: improve binding

Widgets/NSearchableComboBox.qml

@@ -95,6 +95,15 @@ RowLayout {
 
   onSearchTextChanged: filterModel()
   onModelChanged: filterModel()
+  Component.onCompleted: filterModel()
+
+  // Watch for model content changes (e.g., async font loading)
+  Connections {
+    target: root.model
+    function onCountChanged() {
+      filterModel();
+    }
+  }
 
   NLabel {
     label: root.label