refactor: Implement Rectangle tool with snapping and dimensions

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

src/SketchObject.h

@@ -7,7 +7,8 @@ class SketchObject
 {
 public:
     enum class ObjectType {
-        Line
+        Line,
+        Rectangle
     };
 
     SketchObject() = default;