Enable anonymous survey submissions without sign-in prompt

Description: As a survey admin, I want a built-in option to disable the sign-in prompt for survey participants, so they can submit surveys anonymously without interruption. This should be a per-survey setting in Surveys that removes the login pop-up and allows seamless submission for users who are not signed in. Problem: Currently, anonymous users encounter a login pop-up when submitting a survey. Teams rely on a custom widget script workaround to auto-skip this prompt. This adds friction for respondents, complicates setup, and is fragile across updates. Benefit: Native support streamlines anonymous data collection, improves completion rates, reduces maintenance, and ensures consistent behavior across delivery channels without custom code.