feat: Add interactive sketch line drawing to viewport

Co-authored-by: aider (gemini/gemini-2.5-pro) <aider@aider.chat>

src/ApplicationController.h

@@ -3,6 +3,7 @@
 
 #include <QObject>
 #include "ViewportWidget.h" // For SketchPlane enum
+#include <gp_Pnt.hxx>
 
 class Document;
 class MainWindow;
@@ -30,6 +31,7 @@ public:
 
 public slots:
     void setActiveTool(ToolType tool);
+    void addLine(const gp_Pnt& start, const gp_Pnt& end);
     void newDocument();
     bool openDocument();
     bool saveDocument();