Add BooksSyncContext, refine database schema, and enhance synchronization support

- Introduce `BooksSyncContext` for managing book synchronization states (server-only, local-only, to-sync, etc.).
- Remove `UserContext` and related dependencies.
- Refine localization strings (`en.json`) with sync-related updates (e.g., "toSyncFromServer", "toSyncToServer").
- Extend database schema with additional tables and fields for syncing books, chapters, and related entities.
- Add `last_update` fields and update corresponding repository methods to support synchronization logic.
- Enhance IPC handlers with stricter typing, data validation, and sync-aware operations.

lib/models/User.ts

@@ -22,7 +22,6 @@ export interface UserProps {
         openai: boolean,
         anthropic: boolean,
     },
-    books?: BookProps[];
     guideTour?: GuideTour[];
     subscription?: Subscription[];
     writingLang: number;