fix: added dns for existing project to access

[AjitPadhi-Microsoft]

Purpose

• This pull request introduces support for creating a private endpoint for an existing AI service in the infra/main.bicep file. The main goal is to enable secure, private networking for pre-existing Cognitive Services resources, if specified, by provisioning the necessary private endpoint and DNS zone configurations.

Does this introduce a breaking change?

• [ ] Yes
• [x] No

Golden Path Validation

• [ ] I have tested the primary workflows (the "golden path") to ensure they function correctly without errors.

Deployment Validation

• [ ] I have validated the deployment process successfully and all services are running as expected with this change.

What to Check

Verify that the following are valid

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Other Information