refactor: prune orphaned attic modules and standardize project configurations

- Move orphaned modules (data_segment.py, contour_models.py, marching_squares.py) to attic/.
- Standardize local settings logic, serial port parameters, and graph view plots.
- Update pyproject.toml pyside6-project dependencies and configure gitignore.

src/pygui/backend/visualization/graph_view.py

@@ -9,16 +9,13 @@ from __future__ import annotations
 import logging
 from typing import Any, Optional
 
+import pyqtgraph as pg
+from pyqtgraph import PlotWidget
 from PySide6.QtCore import Property, QObject, Signal, Slot
 from PySide6.QtWidgets import QWidget
 
 log = logging.getLogger(__name__)
 
-# Import pyqtgraph after Qt is initialized
-import pyqtgraph as pg
-from pyqtgraph import PlotWidget
-
-
 class GraphView(QObject):
     """QML-exposed controller for a pyqtgraph line chart.