Add Docker + GitHub Actions CI/CD pipeline

[trsdn]

Summary

Containerize the application and set up automated CI/CD with GitHub Actions.

Tasks

• Create \Dockerfile\ for the news app
• Create \docker-compose.yml\ for local development
• Add .dockerignore\ file
• Create GitHub Actions workflow for CI (lint, test, build)
• Add workflow for PR checks
• (Optional) Add workflow for container image publishing

Acceptance Criteria

• \docker build\ creates a working image
• \docker-compose up\ starts the app locally
• GitHub Actions runs on every push/PR
• CI fails if tests or linting fails