Domain redirects: send an address to another, over HTTP and HTTPS

A website resource can now redirect to a full address (301 or 302), optionally
keeping the path and query, with no target or login. The Add resource wizard
has a Domain redirect choice that opens the HTTPS and HTTP sides together.
Deleting a site no longer removes redirects. Uses Reef v0.1.10 and Blacktip v0.1.9.

Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>

infra.go

@@ -270,7 +270,7 @@ func (s *Server) deleteSite(w http.ResponseWriter, r *http.Request, c *orgCtx) {
 			}
 		}
 	}
-	s.st.Mappings = filter(s.st.Mappings, func(m *model.Mapping) bool { return len(m.Targets) > 0 })
+	s.st.Mappings = filter(s.st.Mappings, func(m *model.Mapping) bool { return len(m.Targets) > 0 || m.IsRedirect() })
 	s.bump()
 	s.audit(c.Org.ID, c.Actor, "site.delete", st.Name)
 	ok(w)