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/commands/schematic.py

@@ -1,9 +1,10 @@
-from skip import Schematic
+import logging
 import os
 import shutil
-import logging
 import uuid
 
+from skip import Schematic
+
 logger = logging.getLogger("kicad_interface")