Add backlink outreach prospects by domain or URL

Add one site or a batch of them by hand, for sites you already know are worth pitching. Discovery finds prospects on its own - use outreach_discover for that. New prospects start with no contacts; run outreach_find_people to look them up. Never fails as a whole: unparseable entries and domains already on the list are counted in invalid and skipped, and prospects carries only the rows actually created.