Fix copy path needing one more /contentcuration

[bjester]

Summary

• The refactored Dockerfile copied the wrong directory; both of these exist
  • /contentcuration/contentcuration/static -- referenced by old cruft, misled me, but it's where collectstatic puts all static files eventually
  • /contentcuration/contentcuration/contentcuration/static -- where the frontend assets really live
• We should probably rename the root directory something else like /app or /src to reduce this confusion, although we would need to coordinate that with infra since k8s configs reference this
• The ENTRYPOINT was changed to CMD to facilitate easier inspection, allowing you to launch /bin/bash in it; this should not affect k8s
• The exposed port was changed to align with make altprodserver; k8s uses the same port
• Confusing and unneeded cruft was removed
• Added docker-compose YAML for testing build and startup of the production image

References

Fixes #5754

Reviewer guidance

1. I started up services make dcservicesup
2. I edited the docker-compose.prod.yml to point to the network created by make dcservicesup, e.g.:

networks:
  default:
    name: studio_post-uv-frontend-serve_default
    external: true

3. I ran docker compose -f docker-compose.prod.yml up
4. I accessed http://localhost:8080/
5. While it still wasn't loading all resources (I think this is existing due to config differences), I confirmed that the frontend assets were copied and that it didn't fail to find the serviceWorker.js like the Sentry error

AI usage

I asked AI to help debug it. Ultimately, it didn't help.