I have something close to this, even a helpful bulk import. But it works on your own account not someone else’s.

The feature

https://learnalist.net/faq/add-a-list-overtime-for-spaced-le...

Bulk import ui https://learnalist.net/toolbox/srs-add-overtime-v1.html

You’re welcome to try it, it is not self-hosted.

I also have a mobile app, and have been thinking of how to simplify the server etc.

Equally been thinking about how to modify the mobile app to work better with a different backend but still maintain notifications (local instead of server).

It used to be in the public domain but I moved it to a private repo. I am open to moving it back, there is just a small part of the code I want to keep private.