Fix TOTP manager import and add test

src/password_manager/manager.py

@@ -25,6 +25,7 @@ from password_manager.password_generation import PasswordGenerator
 from password_manager.backup import BackupManager
 from password_manager.vault import Vault
 from password_manager.portable_backup import export_backup, import_backup
+from password_manager.totp import TotpManager
 from utils.key_derivation import (
     derive_key_from_parent_seed,
     derive_key_from_password,