feat: scaffold writing-platform Express + TypeScript backend
- Initialize npm project with express, cors, jsonwebtoken, dotenv, socket.io, openai, uuid
- Configure TypeScript with strict mode, ES2020 target, declarations and source maps
- Create src directory structure: routes/, middleware/, services/, models/
- Add minimal server.ts with health check at /api/writing/health (port 3100)
- Add .gitignore for node_modules, dist, .env
Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>