Versions Destroy

Unified view for single prompt version operations (retrieve/update/delete). Supports both JWT (dashboard) and API key (public API) authentication.

Uses NestedResourceMixin for parent-aware access control:

• READ child = READ parent → superadmin can view any
• WRITE child = WRITE parent → requires org match (for JWT auth)

JWT auth: uses pk lookup API key auth: uses prompt_id + version lookup