iOS standalone/selfhosted CRM app

Hey, I'm looking for some form of CRM to take notes about people I meet.

Feature-wise I would like something like MonicaHQ, but for iPhone use mainly (or only).

I don't want to share my data with a provider for monthly subscription. Therefore app should be standalone (with offline backup or sync via WebDav etc.) or selfhosted. I'm ok with one time purchase.

Does something like this exist?