Add offline mode support with PIN configuration and management

- Introduce `OfflinePinSetup` component for users to configure secure offline access.
- Add new `AIUsageContext` and extend `OfflineProvider` for offline-related state management.
- Implement offline login functionality in `electron/main.ts` with PIN verification and fallback support.
- Enhance IPC handlers to manage offline mode data, PIN setup, and synchronization.
- Update localization files (`en.json`, `fr.json`) with offline mode and PIN-related strings.
- Add `bcrypt` and `@types/bcrypt` dependencies for secure PIN hashing and validation.
- Refactor login and session management to handle offline mode scenarios with improved error handling and flow.

electron/preload.ts

@@ -34,4 +34,12 @@ contextBridge.exposeInMainWorld('electron', {
 
   // Database initialization (shortcut for convenience)
   dbInitialize: (userId: string, encryptionKey: string) => ipcRenderer.invoke('db-initialize', userId, encryptionKey),
+
+  // Offline mode management
+  offlinePinSet: (pin: string) => ipcRenderer.invoke('offline:pin:set', { pin }),
+  offlinePinVerify: (pin: string) => ipcRenderer.invoke('offline:pin:verify', { pin }),
+  offlineModeSet: (enabled: boolean, syncInterval?: number) =>
+    ipcRenderer.invoke('offline:mode:set', { enabled, syncInterval }),
+  offlineModeGet: () => ipcRenderer.invoke('offline:mode:get'),
+  offlineSyncCheck: () => ipcRenderer.invoke('offline:sync:check'),
 });