Recommended architecture? (migrating from Next.js)

[lukasb]

I have a SPA, currently using Next.js. Right now user data is stored on a server.

I'm going to move to local-first, so the app will work without a network connection, and the user only needs to login if they want to sync their content with the server. And obviously I want to wrap this with Tauri to allow native installs. User data will be stored in LocalStorage for PWA users and on the filesystem for Tauri users.

Any recommendations for architecture? For example, I could split my existing Next.js project into two projects, backend (Node) and frontend (React+Vite.) This is kind of a hassle since there's a good deal of shared code, but seems inevitable. Is there a better idea?