feat: add node graphic item

src/gui/network/NodeGraphic.h

@@ -0,0 +1,29 @@
+#pragma once
+#include <QGraphicsItem>
+#include <QPainter>
+
+class NodeGraphic
+: public QGraphicsItem
+{
+public:
+    NodeGraphic(QGraphicsItem *parent = nullptr);
+    QRectF boundingRect() const override
+    {
+        qreal penWidth = 6;
+        return QRectF(-10 - penWidth / 2, -10 - penWidth / 2,
+                      20 + penWidth, 20 + penWidth);
+    }
+
+    void paint(QPainter *painter, const QStyleOptionGraphicsItem *option, QWidget *widget) override
+    {
+        QPen greenPen = QPen(Qt::green);
+        greenPen.setWidth(6);
+        painter->setPen(greenPen);
+
+        painter->drawRoundedRect(-10, -10, 20, 20, 5, 5);
+    }
+
+private:
+    QGraphicsTextItem* title_;
+};
+