bug: user stars still count deleted repos #433

when starring a repository that gets deleted later, the starred repos count on a user's profile still counts the deleted repository.

this seem to happen since the generalize-stars-subject migration: https://tangled.org/tangled.org/core/blob/master/appview/db/db.go#L1188-1189 which removed the foreign key constraint, and the ON DELETE CASCADE associated to it.