Fix undo history dialog text visibility in dark theme

- Change text color from black to white for better contrast against dark gray background
- Update dialog screenshot to reflect improved visibility
- Maintain gray color for undone commands for visual distinction

🤖 Generated with [Claude Code](https://claude.ai/code)

Author: bhowiebkr-lab

images/node_history_dialog.png

@@ -119,7 +119,7 @@ def _populate_history(self):
 
             # Color coding for visual clarity
             if i <= current_index:
-                item.setForeground(Qt.GlobalColor.black)
+                item.setForeground(Qt.GlobalColor.white)
                 if i == current_index:
                     # Current position - make it bold
                     font = item.font()