Billing issues. What happens if the credit card you use to pay for everything gets hijacked, and you're trapped with a blocked card trying to clean it up but your bank is taking their sweet time and won't give you another card until it's sorted? ALWAYS have a backup credit card.
DNS Registrar. There's a hard SPOF in the DNS, where your registrar essentially holds your domain name hostage. If your DNS gets hijacked, but your registrar is taking a few days to sort out who actually owns it, you're down hard. There's no mitigation for this one, except paying for a registrar with proper security processes. If you do 3FA anywhere, make it here.
AppStore. If your app gets banned, or a critical update blocked, what do you do? Building in a fallback URL (using a different domain name, with a different registrar, can help work around any backend issues. There's not much you can do for the frontend functionality, except using a webapp.
It can be worthwhile looking at risks and possible mitigations beyond just server and database issues, especially when it's just you.