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/adminconsole/views.go

@@ -76,6 +76,7 @@ type UserRow struct {
 	Kind            string
 	Language        string
 	Guest           bool
+	Deleted         bool
 	FlaggedHighRate bool
 	CreatedAt       string
 	HasMoveStats    bool