Create template
Create a template. For `*_workflows`, include a `workflow` object.
**Request body fields:**
- `group` (string, required) - Template group identifier (e.g. `account_workflows`).
- `workflow` (object, required for workflow templates) - Contains `name`, `description`, and `body` (nodes + edges graph).
- `body.nodes` (array) - Workflow action nodes (type: `start-node` | `action-node`).
- `body.edges` (array) - Connections between nodes.
- `name` (string, optional on update) - Template display name.