I use synology surveilance station. The cameras are also integrated in homeassistant. I have also integrated the cameras via onvif as a test.
How is it possible for me to receive a notification + image on my iPhone when there is movement?
Initiated by Surveillence station or HA? In both cases yes. But you need to capture image to your HA and than in HA create notification using that saved image.
Part of that is available in my GitHub repo - saving local image when there is motion.