Feature: Delete Workflow Template (API + UI)

[FreeDurok]

Summary

Workflow templates are stored but cannot be removed. Add a simple delete capability.

API (openrelik-server)

• DELETE /workflows/templates/{template_id}
  • 204: deleted
  • 404: not found
  • 409: conflict (e.g., template referenced by active workflows)
  • 400: invalid template_id
• OpenAPI/docs: add endpoint with brief examples.

UI (openrelik-ui)

• Templates list: per-row Delete (trash icon).
• Confirmation dialog: shows template name; requires explicit confirmation.
• After success: show toast, refresh list; removed template no longer visible.
• On errors: map 404/409/400 to concise messages.

Data/Behavior

• Server removes the template record; enforce referential checks.
• No bulk delete in scope.

Acceptance

• Deleting a template via the UI works end-to-end and updates the list.
• API documented; basic e2e and unit tests cover 204/404/409/400 paths.