Remove SyncService and introduce context-based offline mode and state management

- Delete `SyncService` and its associated bidirectional synchronization logic.
- Add multiple context providers (`OfflineProvider`, `AlertProvider`, `LangContext`, `UserContext`, `SessionContext`, `WorldContext`, `SettingBookContext`) for contextual state management.
- Implement `SecureStorage` for OS-level secure data encryption and replace dependency on `SyncService` synchronization.
- Update localization files (`en.json`, `fr.json`) with offline mode and error-related strings.

context/BookContext.ts

@@ -0,0 +1,13 @@
+import {Context, createContext, Dispatch, SetStateAction} from "react";
+import {BookProps} from "@/lib/models/Book";
+
+export interface BookContextProps {
+    book: BookProps | null,
+    setBook?: Dispatch<SetStateAction<BookProps | null>>
+}
+
+export const BookContext: Context<BookContextProps> = createContext<BookContextProps>({
+    book: null,
+    setBook: () => {
+    }
+})