Integrate session management, multilingual IPC handlers, and Book database operations

- Add `LocalSystem` with handlers for session retrieval (`userId`, `lang`) and error handling.
- Extend IPC handlers to support multilingual operations (`fr`, `en`) and session data injection

electron/main.ts

@@ -129,8 +129,19 @@ ipcMain.handle('remove-token', () => {
   return true;
 });
 
-ipcMain.on('login-success', (_event, token: string) => {
+// IPC Handlers pour la gestion de la langue
+ipcMain.handle('get-lang', () => {
+  return store.get('userLang', 'fr');
+});
+
+ipcMain.handle('set-lang', (_event, lang: 'fr' | 'en') => {
+  store.set('userLang', lang);
+  return true;
+});
+
+ipcMain.on('login-success', (_event, token: string, userId: string) => {
   store.set('authToken', token);
+  store.set('userId', userId);
 
   if (loginWindow) {
     loginWindow.close();
@@ -141,6 +152,8 @@ ipcMain.on('login-success', (_event, token: string) => {
 
 ipcMain.on('logout', () => {
   store.delete('authToken');
+  store.delete('userId');
+  store.delete('userLang');
 
   // Close database connection
   const db = getDatabaseService();