Add cad-automation - Zero-cost CAD automation tool

[1036007003-wq]

📋 Description

Add cad-automation to the Physics and Engineering section.

✨ Features

• ✅ Batch process DXF files (convert construction drawings to as-built drawings)
• ✅ Text replacement (support regex)
• ✅ Layer management (batch freeze/thaw)
• ✅ No AutoCAD license required
• ✅ 100% free, open-source (MIT License)

🛠️ Tech Stack

• ezdxf - Pure Python DXF library
• Click - Elegant CLI framework
• Python 3.8+ - Compatible with macOS/Linux/Windows

🔗 Links

• GitHub: https://github.com/1036007003-wq/cad-automation
• Demo: https://1036007003-wq.github.io/cad-automation/
• Documentation: https://github.com/1036007003-wq/cad-automation#readme

✅ Checklist

• I have read the contributing guidelines
• This PR adds a single project (not a list of projects)
• The project is actively maintained
• The project has clear documentation
• The project is open-source (MIT License)