enhancement: Add Azure Policy deployment script

[Daren9m]

Description

Policy JSON definitions exist in policies/ (require-tags.json, deny-unused-resource-types.json) but there is no PowerShell script to deploy them to Azure. The cleanup strategy Phase 3 (Governance) requires deploying policies in Audit mode.

Proposed Script

policies/Deploy-AzurePolicies.ps1 with:

• -Mode parameter: Audit (default) or Deny
• -Scope parameter: subscription or management group
• -WhatIf support
• Deploys both policy definitions and assignments
• Logs deployment results

Acceptance Criteria

• Script deploys policies in Audit mode by default
• -WhatIf shows what would be deployed without making changes
• Can switch to Deny mode with explicit parameter
• Pester tests with mocked Az calls