[FEATURE] Pipedream: Create Workflow API

**Is your feature request related to a problem? Please describe.**
Users can't use Pipedream API to create workflows unless they manually create workflow templates in the admin (this doesn't work for brand new workflows)

**Describe the solution you'd like**
- Add Create Workflow API to Pipedream REST APIs
- Optionally, Improve the GitHub repo sync feature to create new workflow matching the code in Git repo

**Do you have a workaround?**
No

**Additional context**
Raise by a customer here: https://pipedream-users.slack.com/archives/C07EYDZ5S59/p1744741630268269