Migrate from electron-store to OS-level secure storage (getSecureStorage)

- Replace `electron-store` with OS-level encrypted storage for secure token, userId, and language management in `LocalSystem` and `keyManager`.
- Add `init-user` IPC handler to initialize user data and manage encryption keys.
- Update login process to handle encrypted storage saving with fallback for macOS issues.
- Add offline warning component to `login/page.tsx` to handle first-time sync requirements.
- Remove `electron-store` and associated dependencies from `package.json` and `package-lock.json`.

app/page.tsx

@@ -212,6 +212,20 @@ function ScribeContent() {
                     }
                     return;
                 }
+
+                // Initialize user in Electron (sets userId and creates/gets encryption key)
+                if (window.electron && user.id) {
+                    try {
+                        const initResult = await window.electron.initUser(user.id);
+                        if (!initResult.success) {
+                            console.error('[Page] Failed to initialize user:', initResult.error);
+                        } else {
+                            console.log('[Page] User initialized successfully, key created:', initResult.keyCreated);
+                        }
+                    } catch (error) {
+                        console.error('[Page] Error initializing user:', error);
+                    }
+                }
                 setSession({
                     isConnected: true,
                     user: user,