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/SessionContext.ts

@@ -0,0 +1,17 @@
+import {SessionProps} from "@/lib/models/Session";
+import {Context, createContext, Dispatch, SetStateAction} from "react";
+
+export interface SessionContextProps {
+    session: SessionProps;
+    setSession: Dispatch<SetStateAction<SessionProps>>;
+}
+
+export const SessionContext: Context<SessionContextProps> = createContext<SessionContextProps>({
+    session: {
+        isConnected: false,
+        accessToken: "",
+        user: null,
+    },
+    setSession: () => {
+    },
+})