♻️(backend) encapsulate recording key and extension logic as properties

Move logic for calculating recording keys and file extensions into proper
properties on recording objects. Simplifies access to Minio storage keys
and clearly documents expected behavior when saving recordings across the
application.

src/backend/core/recording/event/notification.py

@@ -112,10 +112,8 @@ class NotificationService:
             logger.error("No owner found for recording %s", recording.id)
             return False
 
-        key = f"{settings.RECORDING_OUTPUT_FOLDER}/{recording.id}.ogg"
-
         payload = {
-            "filename": key,
+            "filename": recording.key,
             "email": owner_access.user.email,
             "sub": owner_access.user.sub,
         }