Migrate data-art to Node.js/TypeScript web app with Docker Compose deployment

[Copilot]

The existing Python CLI-only application needs to run as a web service on a Hetzner VPS, deployable via Docker Compose alongside other services.

Changes

web/ — Node.js + TypeScript application

• src/core.ts — port of the text→pixel→PNG algorithm using pngjs (no native deps)
• src/server.ts — Express server exposing three endpoints:
  • POST /api/generate — accepts { text } JSON, returns PNG buffer
  • GET / — serves the browser UI
  • GET /health — liveness probe for container orchestration
• src/core.test.ts — 16 Jest unit tests mirroring the Python test suite
• public/index.html — self-contained dark-themed UI: textarea → generate → inline preview + PNG download

Container

• web/Dockerfile — multi-stage Node 20 Alpine build; non-root user; wget-based HEALTHCHECK
• docker-compose.yml (repo root) — single service definition, restart: unless-stopped

# Deploy
docker compose up --build -d
# → http://<host>:3000

# API usage
curl -X POST http://localhost:3000/api/generate \
  -H "Content-Type: application/json" \
  -d '{"text":"To be or not to be"}' --output out.png

The original Python CLI and its Dockerfile are kept untouched.