An implementation for Svelte is already planned, but thank you for the recommendation. I'll move the codebase of the Angular implementation into a seperate project soon which will make integrations for other JS frameworks pretty easy.
Your project looks very interesting and I'll definitely take a look into it.
The support for graph data is still in consideration. Offline/Local first support is planned and will definitely be a feature in the future.
The credentials you found in the app.module.ts are just credentials to identify the client (not the user). It is just to give an extra layer of security and only allow specific applications access to the server. User authentication is handled through tokens for example.
The architecture looks more like this:
Client -> Asp.Net Core server with SapphireDb -> any database server
SapphireDb is not a database. Its more like the connector between database and clients. Because of that there is no package for a NodeJS because it would just be proxy.
Yes I think it is production ready. I'll add a section in the docs describing the criteria this opinion is based on.