OAuth 2.0 authorization server

Design an OAuth 2.0 / OIDC authorization server that lets thousands of third-party apps (web, mobile, SPA, server-to-server) request scoped access to your users' data. Requirements: users grant granular consent and can revoke an app's access anytime; tokens are scoped and short-lived; and you must safely support public clients (mobile/SPA) that can't keep a secret. Walk through the flows you'd support and why, how scopes and consent are stored and enforced, and how revocation works when a user removes an app.