fix(admin): unified user search across live + deleted, incl. the retention journal

The email/name/external-id search was scoped to one tab and only looked in the live
identities table, so a deleted account (whose credentials moved to retained_identities on
deletion) could not be found by the email/id it held. Now a people search spans live and
deleted accounts in one query (robots only on the Robots tab) and also matches the
retention journal and the retained real name; results carry a 'deleted' badge. Integration
test: a deleted account is found by its held email and external id.

backend/internal/server/handlers_admin_console.go

@@ -170,14 +170,17 @@ func (s *Server) consoleUsers(c *gin.Context) {
 	ids := make([]uuid.UUID, 0, len(items))
 	for _, it := range items {
 		kind := "registered"
-		if it.IsRobot {
+		switch {
+		case it.IsRobot:
 			kind = "robot"
-		} else if it.IsGuest {
+		case it.IsDeleted:
+			kind = "deleted"
+		case it.IsGuest:
 			kind = "guest"
 		}
 		view.Items = append(view.Items, adminconsole.UserRow{
 			ID: it.ID.String(), DisplayName: it.DisplayName, Kind: kind,
-			Language: it.PreferredLanguage, Guest: it.IsGuest,
+			Language: it.PreferredLanguage, Guest: it.IsGuest, Deleted: it.IsDeleted,
 			FlaggedHighRate: !it.FlaggedHighRateAt.IsZero(), CreatedAt: fmtTime(it.CreatedAt),
 		})
 		ids = append(ids, it.ID)