Added dependency injection for `AuthService` to enable authentication-related operations. Introduced a logout button in the UI, conditionally displayed when `EnvelopeKey` is valid, with a spinner and SVG icon for better UX.
Implemented the `LogoutAsync` method to handle the logout process, ensuring no concurrent logouts and redirecting the user to the login page. Added `_isLoggingOut` to manage logout state. Updated `OnInitializedAsync` for better error handling when `EnvelopeKey` is missing.