feat: Add devcontainer configuration for n8n-workflows development

- Configure Claude Code optimized devcontainer with Python support
- Add Python development tools (black, flake8, isort) to Dockerfile
- Include VS Code extensions for Python and workflow development
- Add firewall script for secure development environment
- Update .gitignore to exclude Claude Code local settings

🤖 Generated with [Claude Code](https://claude.ai/code)

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

.gitignore

@@ -87,4 +87,7 @@ package-lock.json
 *.db-wal
 
 # versions
-.python-version
+.python-version
+
+# Claude Code local settings (created during development)
+.claude/settings.local.json