- Delete `data.service.ts` and `offline-data.service.ts`, consolidating functionality into `LocalSystem`.
- Refactor book, character, and conversation operations to adopt unified, multilingual, and session-enabled IPC handlers in `LocalSystem`.
- Simplify redundant legacy methods, enhancing maintainability and consistency.
- Implement `schema.ts` for SQLite schema creation, indexing, and sync metadata initialization.
- Develop `encryption.ts` with AES-256-GCM encryption utilities for securing database data.
- Add `database.service.ts` to manage CRUD operations with encryption support, user-specific databases, and schema initialization.
- Integrate book, chapter, and character operations with encrypted content handling and sync preparation.
- Add services for offline data management, including `offline-data.service.ts`, ensuring data is saved to a local database and synced with the server when online.
- Introduce bidirectional `SyncService` for managing data synchronization with conflict resolution and retry mechanisms.
- Create `data.service.ts` to handle smart routing between local database and server API based on connectivity status.
- Update models and logic to support comprehensive synchronization for books, chapters, characters, and conversations.
- Implement event listeners for online/offline detection and automatic sync scheduling.
