fix: correct device cache key format in DeviceUpdate

Fix inconsistent cache key format by using "device/${uid}" instead of
"device${uid}/" to match the expected cache key pattern used elsewhere
in the codebase.

Author: heiytor

api/store/mongo/device.go

@@ -450,7 +450,7 @@ func (s *Store) DeviceUpdate(ctx context.Context, tenantID, uid string, changes
 		return store.ErrNoDocuments
 	}
 
-	if err := s.cache.Delete(ctx, "device"+uid+"/"); err != nil {
+	if err := s.cache.Delete(ctx, "device"+"/"+uid); err != nil {
 		logrus.WithError(err).WithField("uid", uid).Error("cannot delete device from cache")
 	}