fix import issue when running gui entry point

charon_vna/gui.py

@@ -24,10 +24,10 @@ from PySide6.QtWidgets import (
     QVBoxLayout,
     QWidget,
 )
-from vna import Charon
 
 from charon_vna.plots import PlotWidget
 from charon_vna.util import net2s, s2net
+from charon_vna.vna import Charon
 
 # %%
 DEFAULT_CONFIG = Path(__file__).parent / "config_default.json"