Remove conditional from Azure login step in deployment workflow

[Copilot]

This PR simplifies the Azure deployment workflow by removing conditional logic from the authentication steps and consolidating to a single login method using Federated Credentials.

Changes Made

Before:

• Two conditional login steps:
  • Log in with Azure (Federated Credentials) with if: ${{ env.AZURE_CLIENT_ID != '' }}
  • Log in with Azure (Client Credentials) with if: ${{ env.AZURE_CREDENTIALS != '' }}

After:

• Single unconditional login step using Federated Credentials:

- name: Log in with Azure (Federated Credentials)
  run: |
    azd auth login `
      --client-id "$Env:AZURE_CLIENT_ID" `
      --federated-credential-provider "github" `
      --tenant-id "$Env:AZURE_TENANT_ID"
  shell: pwsh

Benefits

• Simplified workflow logic: Eliminates conditional authentication branching
• Reduced complexity: Removes potential failure points from dual authentication paths
• Consistent authentication: Uses only Federated Credentials (current best practice)
• Follows GitHub Actions best practices: Aligns with recommended patterns for Azure authentication

Impact

• Minimal change: 0 lines added, 15 lines removed
• No functional impact on successful deployments using Federated Credentials
• YAML syntax validated and confirmed working

Fixes #296.

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