Support for password-protected PDFs

When users try to preview password-protected PDF file in encrypted email message, they get error `Error downloading file - PasswordException: No password given.`. To fix it, let's show alert asking for pdf password in such cases

<img width="400" height="164" alt="Image" src="https://github.com/user-attachments/assets/d0d6f300-5191-4c0e-b01d-8765185af08e" />