fix(events): keep registration status reads nonblocking

apps/notifications/services.py

@@ -88,6 +88,10 @@ class RedisNotificationStore:
 
     @classmethod
     def add(cls, user_id: str, payload: dict) -> dict:
+        if payload.get("id"):
+            existing = cls.get(user_id, str(payload["id"]))
+            if existing:
+                return existing
         data = cls._normalize_notification(payload)
         created_at = parse_datetime(data["created_at"]) or timezone.now()
         created_at_ts = created_at.timestamp()