Show only feedback within a specified public date range

Description: Add an option to define a public visibility date range so only feedback items within a specified start and end date/time are shown on public pages, embeds, and public APIs. Problem: Currently, all feedback may appear publicly regardless of age, causing outdated or premature content to be visible. This limits time-bound campaigns, seasonal announcements, and compliance needs (e.g., hiding items before/after a specific window) and requires manual moderation. Benefit: A configurable visibility window enables relevant, time-bound displays with less manual work. It improves user trust by hiding stale items, supports campaigns and compliance, and creates consistent behavior across public surfaces and APIs.