[sifnode] Add AKS deployment scaffolding and Azure provider support

[AJ0070]

This PR adds Azure AKS deployment support for sifnode while preserving the existing AWS-oriented deployment shape.

What Changed

• added a deploy/ deployment workflow back into the repo with:
  • Rake tasks for cluster scaffold, deploy, destroy, and Helm-based sifnode deploys
  • a Helm chart for sifnode
  • Terraform provider modules for both AWS and Azure
  • Terraform templates for aws and azure
• added Azure provider selection support in the CLI-style Rake flow
  • supported values: azure and az
• added AKS Terraform support under deploy/terraform/providers/azure
• updated the Helm chart to be cloud-aware
  • AWS keeps AWS-specific load balancer annotations
  • Azure defaults PVCs to managed-csi
• added AKS setup and deployment documentation in docs/tutorials/running-sifchain-validator-on-aks.md
• updated Terraform templates to expose kubectl_config so the deployment flow can persist kubeconfig automatically

Validation

Validated against a real AKS cluster in Azure:

• terraform init
• terraform validate
• terraform plan
• terraform apply
• helm upgrade --install
• verified:
  • AKS cluster creation
  • PVC provisioning on Azure Disk CSI
  • LoadBalancer service allocation
  • sifnode pod reached Running
  • node logs showed blocks being executed and committed

Notes

• this PR includes .gitignore changes so the new deploy/ tree is actually tracked
• the deployment workflow is intentionally aligned with the older AWS pattern referenced in the issue, while extending it for Azure

fixes #503

[AJ0070]

@sauravtom Can you review this? I have tested this on Azure since I had credits from my student subscription.