[Feature Request] Enable Template Sync Functionality in OneDesign Plugin

[vishal4669]

Summary

The OneContent plugin currently supports syncing of post types and taxonomies across brand sites from the main site.
We now need to extend this capability to include template sync so that brand sites remain fully consistent in terms of layout and design.

Acceptance Criteria

• Creating or updating a template on the main site automatically syncs it to all connected brand sites.
• Admins can toggle template sync on/off.