feat(docker): add Dockerfile & CI/CD workflow for Docker image support

[Programmer-RD-AI]

Closes #83

What’s Changed

• .dockerignore

  • Excludes node_modules, build artifacts, environment files, and other unwanted files from the Docker context.

• Dockerfile

  • Implements a multi-stage build using Node.js 18-alpine for a minimal final image.
  • Deps stage installs dependencies via pnpm or npm ci based on the lockfile.
  • Builder stage compiles the Next.js app and ensures the public directory exists.
  • Runner stage sets up a non-root nextjs user, copies only the standalone build (.next/standalone) and static files, and exposes port 3000.

• GitHub Actions (.github/workflows/docker-publish.yml)

  • Trigger: push to main

  • Steps:

    1. Checkout code
    2. Setup Docker Buildx
    3. Log in to Docker Hub (uses DOCKERHUB_USERNAME & DOCKERHUB_TOKEN secrets)
    4. Build & push programmerrdai/agent-ui:latest

• Miscellaneous fixes

  • Renamed workflow for clarity.
  • Updated environment variable handling and default port exposure.
  • Deduplicated devIndicators entry in next.config.ts.

How to Test

# Build the image locally
docker build -t agent-ui .

# Run the container
docker run -p 3000:3000 agent-ui

# Then visit http://localhost:3000 to verify the app loads correctly