feat(touch): add iconSize property to ModernControlButton

Allows independent control of icon size vs text size.
Usage: iconSize: 24 (defaults to fontSize + 2 if not set)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

dune-weaver-touch/qml/components/ModernControlButton.qml

@@ -9,6 +9,7 @@ Rectangle {
     property color buttonColor: "#2196F3"
     property bool enabled: true
     property int fontSize: 16
+    property int iconSize: -1  // -1 means use fontSize + 2
 
     signal clicked()
 
@@ -51,7 +52,7 @@ Rectangle {
         
         Text {
             text: parent.parent.icon
-            font.pixelSize: parent.parent.fontSize + 2
+            font.pixelSize: parent.parent.iconSize > 0 ? parent.parent.iconSize : parent.parent.fontSize + 2
             color: "white"
             visible: parent.parent.icon !== ""
         }