Refactor imports, streamline database IPC handlers, and improve offline support

- Replace absolute import paths with relative paths for consistency across files.
- Transition database operations in Electron main process to modular handlers in `ipc/book.ipc.ts` using the `createHandler` pattern.
- Update database sync service to use `window.electron.invoke()` for improved reliability and structure.
- Refactor `AddNewBookForm` to handle both online and offline book creation seamlessly.

electron/database/models/User.ts

@@ -1,7 +1,7 @@
-import UserRepo, {UserAccountQuery, UserInfosQueryResponse} from "@/electron/database/repositories/user.repository";
-import System from "@/electron/database/System";
-import Book, {BookProps} from "@/electron/database/models/Book";
-import {getUserEncryptionKey} from "@/electron/database/keyManager";
+import UserRepo, {UserAccountQuery, UserInfosQueryResponse} from "../repositories/user.repository.js";
+import System from "../System.js";
+import Book, {BookProps} from "./Book.js";
+import {getUserEncryptionKey} from "../keyManager.js";
 
 interface UserAccount{
     firstName:string;