Block prospects' sites

Remove one or more prospects and stop them ever coming back from discovery. Use this for sites the user does not want to be associated with; to merely deprioritise one, leave it alone instead. An ordinary site is blocked by domain, so removed can exceed the number of ids you sent when it has several rows. A prospect on a creator platform (a YouTube channel, a Substack) blocks only that creator, leaving the rest of the platform discoverable.