✨(backend) enable retrieve viewset on recording model

Add Django built-in mixins to recording viewset to support individual record
retrieval. Enables frontend to access single recording details needed for
the upcoming download page implementation.

src/backend/core/api/viewsets.py

@@ -544,6 +544,7 @@ class ResourceAccessViewSet(
 class RecordingViewSet(
     mixins.DestroyModelMixin,
     mixins.ListModelMixin,
+    mixins.RetrieveModelMixin,
     viewsets.GenericViewSet,
 ):
     """