feat(deploy): add PowerShell ports of deployment scripts

[WilliamBerryiii]

Summary

Add PowerShell 7+ ports of existing bash deployment helpers for cross-platform compatibility.

Scope

• az-sub-init.ps1 — Azure subscription initialization: validate az CLI, check session/token, handle tenant-scoped login, set ARM_SUBSCRIPTION_ID
• defaults.ps1 — Configuration defaults for 002-setup scripts: Helm chart versions, Kubernetes namespaces, secret names, timeouts, Helm repos, AzureML extension config, OSMO component names, workload identity, GPU instance type, and dataset config. Use $env:VAR ?? 'default' pattern for environment variable overrides.
• terraform-outputs.ps1 — Shared library with Read-TerraformOutputs / Get-TerraformOutput core functions and typed accessor functions for all Terraform outputs

Deliverables

• deploy/000-prerequisites/az-sub-init.ps1
• deploy/002-setup/defaults.ps1
• scripts/lib/terraform-outputs.ps1

Related

Part of HVE-Core migration work tracked in #52.