[Module Proposal]: `avm-ptn-unified-data-platform`

### Check for previous/existing GitHub issues/module proposals

- [x] I have checked for previous/existing GitHub issues/module proposals.

### Check this module doesn't already exist in the module indexes

- [x] I have checked that this module doesn't already exist in the module indexes.

### Bicep or Terraform?

Terraform

### Module Classification?

Pattern Module

### Module Name

avm-ptn-unified-data-platform

### Module Details

Implements the Cloud Adoption Framework's [layered landing-zone pattern for a unified data platform](https://learn.microsoft.com/en-us/azure/cloud-adoption-framework/data/architecture-azure-landing-zones-unify-data-platform), composing a data-management landing zone (Microsoft Fabric capacity + tenant settings) with sibling data landing zones for Fabric domains/workspaces and Azure Databricks, using OneLake as the shared analytical layer between them. Deploys resource groups, Fabric capacity (via `Azure/terraform-azurerm-avm-res-fabric-capacity`), Fabric domains/workspaces/RBAC, optional workspace private link, and a VNet-injected Databricks workspace with an Access Connector (via `Azure/terraform-azurerm-avm-res-databricks-accessconnector`) for OneLake federation.

### Do you want to be the owner of this module?

Yes

### Module Owner's GitHub Username (handle)

bramcal

### (Optional) Secondary Module Owner's GitHub Username (handle)

benvbr

Start by reviewing the linked Cloud Adoption Framework layered landing-zone pattern and the referenced Azure Verified Modules for Fabric capacity and Databricks Access Connector. Use the proposed module name, avm-ptn-unified-data-platform, as the entry point; done means the Terraform pattern composes the described management and data landing zones, Fabric resources, and Databricks integration.

Written by the indexing model from the issue text.