- Added support for creating books locally when the cloud limit is reached.
- Enhanced error handling in `AddNewBookForm` with `ApiError` and fallback logic for local book creation.
- Implemented `BookTypeLimit` to manage type-specific book limits with visual indicators in `BookList`.
- Refactored `TombstoneRecord` to standardize naming conventions for better API compatibility.
- Updated `useSyncSeries` and `useSyncBooks` to handle empty tombstones gracefully.
- Updated locales with new translations for fallback and error messaging.
- Replaced legacy vault key derivation with OS keyring-backed storage for improved security and platform integration.
- Introduced PIN rate limiting with configurable lockout durations to mitigate brute-force attacks.
- Enhanced tombstone services to use unified error-handling logic via `apply_tombstone`.
- Refactored logic for book and series data synchronization, fixing null checks and improving flow consistency.
- Added comprehensive error handling to all database and vault operations in key manager services.
- Replaced `window.electron.invoke` calls with equivalent `tauri` function calls for all IPC interactions.
- Removed `electron.d.ts` TypeScript definitions as they are no longer needed.
- Updated related logic for offline/online state synchronization.
- Added `types.rs` and `shared/mod.rs` modules to support Tauri IPC integration with Rust enums and shared logic.
- Refactored IPC request queues to use updated handler names for consistency with Tauri.
