fix: backend prod dockerfile

[Nabhag8848]

Description

• includes environment variables as ARG in dockerfile so railways env will be used in container.
  https://docs.railway.app/guides/dockerfiles#using-variables-at-build-time

Fixes # (issue)

• New feature (non-breaking change which adds functionality)

Checklist:

• My code follows the style guidelines of this project
• I have performed a self-review of my code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• My changes generate no new warnings

[vercel]

@Nabhag8848 is attempting to deploy a commit to the OpenInt Team on Vercel.

A member of the Team first needs to authorize it.

[github-actions]

Thank you for following the naming conventions for pull request titles! 🙏