bug: deleted contacts keep private payments and can reappear

Twin: synonymdev/bitkit-ios#838
Refs: synonymdev/bitkit-android#1372

### What happened?

After deleting a contact, its private payment links stayed available, and a deleted contact could reappear after a successful deletion.

### Expected behavior

Deleting a contact revokes its private payment links, and the contact stays deleted until the user adds or imports it again.