Anyone can sign in. Authentication is handled by Cloudflare Access.
Cloudflare Access verifies who you are before the app even loads. There is no password for Skim to store, and no account to create.
Items are stored in Cloudflare D1 and scoped to your identity, so you only ever see and change your own list.
Static pages and API routes both run on Cloudflare's edge network, close to wherever you happen to be.