Move mail, compose, contacts, and accounts off mocks onto REST + WS.
Add client, auth store, IDB-backed query cache, offline queue, and
sync bar; hybrid Zustand for UI-only state. Settings still local until
backend has preferences API.
- Introduced CSS animations for splash screen elements including aurora drift, logo float, loader progress, and card breathing effects.
- Implemented a new FirstLaunchSplash component in layout to display the splash screen on the initial app launch.
- Updated theme initialization script to manage splash screen visibility based on local storage state.
