style: ruff format and the lint rules of the driver standard

Mechanical: ruff format, and ruff check --fix with the rule set every NAPALM
driver uses (E, F, I, UP, B at line length 100, Python 3.10). What ruff
cannot fix comes in the next commit.

tests/conftest.py

@@ -2,11 +2,11 @@
 
 from __future__ import annotations
 
-import pytest
 from unittest.mock import MagicMock, patch
 
-from napalm_proxmox.driver import ProxmoxDriver
+import pytest
 
+from napalm_proxmox.driver import ProxmoxDriver
 
 # ---------------------------------------------------------------------------
 # Sample API payloads
@@ -124,6 +124,7 @@ PVE_USERS = [
 # Driver fixture
 # ---------------------------------------------------------------------------
 
+
 def _build_mock_api(
     nodes=None,
     node_status=None,