add multi-stage Dockerfile with nginx for production deployment

[thuantan2060]

📝 Pull Request Summary

Add a production-ready Docker setup using multi-stage build (Node.js build → nginx serve) with API reverse proxy
configuration for the memU server backend.

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✅ What does this PR do?

• Add Dockerfile with multi-stage build:
  • Stage 1 (builder): node:22-alpine installs dependencies and runs npm run build to produce optimized
    static assets via Vite
  • Stage 2 (runtime): nginx:alpine serves the built files (~25MB final image vs ~1GB with node_modules)
• Add nginx.conf with:
  • Reverse proxy: /api/* requests forwarded to memu-server:8000 (Docker network), rewriting the /api
    prefix — matches the Vite dev proxy behavior
  • SPA fallback: try_files $uri $uri/ /index.html for client-side routing
  • Static asset caching: 1-year immutable cache headers for JS/CSS/images/fonts
• Add .dockerignore to exclude node_modules, dist, .git from build context

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🤔 Why is this change needed?

• The project currently only supports local development via npm run dev with Vite's built-in proxy
• There is no way to deploy the UI in a containerized environment alongside the memU server
• This enables running the full memU stack (server + UI) via docker compose up with a single command
• The nginx proxy configuration mirrors the Vite dev proxy (/api → backend), so the React app works
  identically in both environments without code changes

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🔍 Type of Change

Please check what applies:

• Bug fix
• New feature
• Documentation update
• Refactor / cleanup
• Other (please explain)

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✅ PR Quality Checklist

• PR title follows the conventional format (feat:, fix:, docs:)
• Changes are limited in scope and easy to review
• Documentation updated where applicable
• No breaking changes (or clearly documented)
• Related issues or discussions linked

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📌 Optional

• Edge cases considered
  • SPA routing: all non-file paths fall back to index.html so React Router works
  • API proxy: strips /api prefix to match backend routes (/api/retrieve → /retrieve)
  • Docker network: nginx resolves memu-server hostname via Docker Compose service discovery
  • Build optimization: multi-stage keeps final image minimal (nginx:alpine ~40MB vs node:22 ~1GB)
• Follow-up tasks mentioned
  • Consider adding VITE_API_BASE_URL build arg for custom API endpoints in non-Docker deployments
  • Consider adding gzip compression in nginx config for additional performance