en-platform-engineer (tenant accounts): Deploy to all tenant production accounts

## Summary

Deploy the validated `en-platform-engineer` role to all active tenant production accounts.

## Tasks

- [ ] Deploy role to each active tenant prod account via Terraform
- [ ] Confirm role is functional in each account
- [ ] Sign-off from SA and EN teams

## Dependencies

Blocked by testing task for this theme.

## Parent Theme

Part of #233