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/Book.ts

@@ -18,8 +18,7 @@ import fs from "fs";
 import BookRepo from "../repositories/book.repository.js";
 import Chapter, {ActChapter, ChapterContentData, ChapterProps} from "./Chapter.js";
 import UserRepo from "../repositories/user.repository.js";
-import ChapterRepo from "@/electron/database/repositories/chapter.repository";
-import {mainStyle} from "@/electron/database/models/EpubStyle";
+import ChapterRepo from "../repositories/chapter.repository.js";
 
 export interface BookProps{
     id:string;