style: apply Black formatting to all Python files

Add [tool.black] config to pyproject.toml and Black hook to
.pre-commit-config.yaml (rev 26.3.1), then auto-format all Python
source and test files with line-length=100, target-version=py310.

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

python/schemas/__init__.py

@@ -4,4 +4,4 @@ Tool schema definitions for KiCAD MCP Server
 
 from .tool_schemas import TOOL_SCHEMAS
 
-__all__ = ['TOOL_SCHEMAS']
+__all__ = ["TOOL_SCHEMAS"]