docs: add template_id attribute to project overview

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

Author: pushya22

docs/api-reference/project/overview.md

@@ -131,6 +131,10 @@ Projects organize your team's work within a workspace. Each project contains wor
 
   Default state which will be used when the issues will be auto closed
 
+- `template_id` _uuid_
+
+  UUID of the project template used to create this project.
+
 </div>
 <div class="api-right">