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.

components/book/AddNewBookForm.tsx

@@ -27,7 +27,7 @@ import GuideTour, {GuideStep} from "@/components/GuideTour";
 import {UserProps} from "@/lib/models/User";
 import {useTranslations} from "next-intl";
 import {LangContext, LangContextProps} from "@/context/LangContext";
-// TODO: Refactor to use window.electron.invoke() instead of OfflineDataService
+import OfflineContext, {OfflineContextType} from "@/context/OfflineContext";
 
 interface MinMax {
     min: number;
@@ -39,6 +39,7 @@ export default function AddNewBookForm({setCloseForm}: { setCloseForm: Dispatch<
     const {lang} = useContext<LangContextProps>(LangContext);
     const {session, setSession} = useContext(SessionContext);
     const {errorMessage} = useContext(AlertContext);
+    const {isCurrentlyOffline} = useContext<OfflineContextType>(OfflineContext);
     const modalRef: React.RefObject<HTMLDivElement | null> = useRef<HTMLDivElement>(null);
     
     const [title, setTitle] = useState<string>('');
@@ -123,7 +124,6 @@ export default function AddNewBookForm({setCloseForm}: { setCloseForm: Dispatch<
         }
         setIsAddingBook(true);
         try {
-            const offlineDataService = getOfflineDataService();
             const bookData = {
                 title,
                 subTitle: subtitle,
@@ -134,26 +134,25 @@ export default function AddNewBookForm({setCloseForm}: { setCloseForm: Dispatch<
                 desiredWordCount: wordCount
             };
 
-            const bookId: string = await offlineDataService.createBook(
-                bookData,
-                session.user?.id || '',
-                async () => {
-                    // Only called if online
-                    const id = await System.authPostToServer<string>('book/add', {
-                        title: title,
-                        subTitle: subtitle,
-                        type: selectedBookType,
-                        summary: summary,
-                        serie: 0,
-                        publicationDate: publicationDate,
-                        desiredWordCount: wordCount,
-                    }, token, lang);
-                    if (!id) {
-                        throw new Error(t('addNewBookForm.error.addingBook'));
-                    }
-                    return id;
+            let bookId: string;
+            if (!isCurrentlyOffline()) {
+                // Online - call API server
+                bookId = await System.authPostToServer<string>('book/add', {
+                    title: title,
+                    subTitle: subtitle,
+                    type: selectedBookType,
+                    summary: summary,
+                    serie: 0,
+                    publicationDate: publicationDate,
+                    desiredWordCount: wordCount,
+                }, token, lang);
+                if (!bookId) {
+                    throw new Error(t('addNewBookForm.error.addingBook'));
                 }
-            );
+            } else {
+                // Offline - call local database
+                bookId = await window.electron.invoke<string>('db:book:create', bookData);
+            }
 
             const book: BookProps = {
                 bookId: bookId,