Update config, docs and add box model

- server.py: Output-Verzeichnis default auf models/ relativ zu server.py
- README.md: Claude Code statt Desktop, models/-Ordner, korrekte settings.json
- models/box.py: Offene Box 30x30x20mm, alle Maße als Variablen

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

server.py

@@ -13,7 +13,8 @@ from mcp.server.fastmcp import FastMCP
 import cadquery as cq
 from cadquery import exporters
 
-OUTPUT_DIR = Path(os.environ.get("CADQUERY_OUTPUT_DIR", Path.home() / "3d-models"))
+_default_output = Path(__file__).parent / "models"
+OUTPUT_DIR = Path(os.environ.get("CADQUERY_OUTPUT_DIR", _default_output))
 OUTPUT_DIR.mkdir(parents=True, exist_ok=True)
 
 mcp = FastMCP("cadquery")