Update project configuration and dependencies

- Added `.vscode` to `.gitignore` to exclude Visual Studio Code settings.
- Updated `pyproject.toml` to include `ruff` for linting and configured its settings.
- Modified `uv.lock` to include `ruff` in both optional and development dependencies.
- Refactored type hints in several files to use `str | None` for optional parameters.
- Cleaned up unused imports and whitespace in various modules for improved code clarity.

tests/test_units.py

@@ -1,10 +1,9 @@
 import pytest
-
 from conftest import load
+
 from oxi.exception import OxiAPIError
 from oxi.interfaces import device_registry
 from oxi.interfaces.base import BaseDevice
-from oxi.interfaces.contract import Interfaces, System
 from oxi.interfaces.utils import decode_utf, expand_vlan_range