bug: error preparing Blob/File data to be stored in object store

### Issue

iOS + Capacitor + Pouch - attachments storage causes intermittent app crash:

> error preparing Blob/File data to be stored in object store

Related issues:

(latest): https://github.com/dexie/Dexie.js/issues/1919
https://github.com/dexie/Dexie.js/issues/1227
https://bugs.webkit.org/show_bug.cgi?id=188438
https://github.com/localForage/localForage/issues/834

As in the top link, storing attachments into indexedDB as **non blob** e.g. B64 appears to resolve the issue (though less efficient). I cannot see an obvious way to more directly tell pouch in a given environment to not use blob storage.

### Info

- Environment: Capacitor iOS
- Platform: Safari WebKit
- Adapter: indexeddb (I think)
- Server: CouchDB

### Reproduce

We are seeing the issue intermittently and cannot reliably recreate.