[Enhancement]: Add reference architectures for cloud provider deployments

### Page or section

https://docs.stacklok.com/toolhive/guides-k8s/

### What could be better?

<img width="594" height="276" alt="Image" src="https://github.com/user-attachments/assets/0ebc9fe8-fb04-4862-8220-7eea4d51f448" />

Provide reference architectures for operator deployments to GKE, EKS, and AKS.

### Proposed improvement

_No response_

### Additional context

_No response_