fix: replace simulated AuthPortal with real passkey/OAuth sign-in

feat: implement passkey auth, OAuth, Paddle payments, and email DI

feat: replace simulated features with real implementations

feat: implement unique guest accounts via device UUID and claiming flow

fix: resolve QR scanner and shared link routing issues by parsing full href and fixing activeDocId race condition

feat: add close buttons to Folder Sidebar, Sync Logs, AI Panel, and Live Preview

refactor: Modularize frontend App.tsx into custom hooks and components and resolve Vite import.meta types