style: sort Python imports with isort

Add isort configuration (profile=black, line_length=100) to pyproject.toml,
add isort pre-commit hook, and auto-sort imports across all Python source files.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

python/tests/test_freerouting.py

@@ -15,12 +15,11 @@ from pathlib import Path
 from unittest.mock import MagicMock, patch
 
 import pytest
-
 from commands.freerouting import (
     FreeroutingCommands,
-    _find_java,
-    _find_docker,
     _docker_available,
+    _find_docker,
+    _find_java,
     _java_version_ok,
 )