Improve documentation for Docker Compose publishing

### Is there an existing issue for this?

- [x] I have searched the existing issues

### Is your feature request related to a problem? Please describe the problem.

I am trying to use Aspire with my CI (TeamCity) to push to a custom private registry (powered by Harbor).

Currently, TeamCity builds each image. Previously I was using Dockerfiles, now I am using .NET SDK with csproj properties. This allows a ``dotnet publish`` to push to my private registry on publish. TeamCity then triggers a Portainer webhook to re-pull the images on our server.

However, this conflicts with ``aspire do prepare-compose`` as outlined in #14075.

``aspire do prepare-compose`` allows building the images locally but all documentation currently seems to assume you will deploy the build artifacts via SSH.

### Describe the solution you'd like

It would be beneficial if we could either:
- Allow pushing to a remote registry depending on the environment specified (eg staging and prod, but not dev)
- Add documentation on pushing to a remote registry after running ``aspire do prepare-compose``

### Additional context

_No response_