Rename models.py to state.py to avoid conflict with models/ directory

The models.py file conflicts with the models/ subdirectory when
importing. Renamed to state.py for clarity.

src/py_dvt_ate/simulation/physics/engine.py

@@ -9,7 +9,7 @@ from __future__ import annotations
 
 from typing import TYPE_CHECKING
 
-from py_dvt_ate.simulation.physics.models import ElectricalState, ThermalState
+from py_dvt_ate.simulation.physics.state import ElectricalState, ThermalState
 
 if TYPE_CHECKING:
     from py_dvt_ate.simulation.physics.models.base import DUTModel