Api Foundation Models Retrieve

Foundation model detail by PK. Auth optional — API key OR JWT parsed if present, anonymous allowed. Serializer filters variants by org when authenticated. Uses ``OptionalJWTAndAPIKeyAuthenticationViewMixin`` (not bare ``authentication_classes=[KeywordsAIJWTAuthentication]``): SimpleJWT raises ``InvalidToken`` (401) on any present-but-non-JWT bearer — i.e. an API key — so the bare config 401'd legitimate API-key callers despite ``AllowAny``. The mixin accepts API key OR JWT and treats unparseable creds as anonymous, and IP-rate-limits anonymous callers via ``TokenBucketThrottle``.