DashboardQuery eager-loads workshop_host with :sponsors in one join (same host-loss trap as #2975) #2982

DashboardQuery.upcoming_events eager-loads :workshop_host together with :sponsors in one join (app/queries/dashboard_query.rb:5-6). Both associations route through the workshop_sponsors table, so the scoped has_one falls into the same eager-load alias trap documented in #2975: workshop_host comes back nil or points at a non-host sponsor, on a plan-dependent subset of workshops.

Suggested fix: the same pattern the events listing now uses (#2981, Listable.most_recent) — keep :sponsors in the join, move the host to preload:

Workshop.eager_load(:chapter, :sponsors, :organisers, :permissions)
        .preload(workshop_host: :sponsor)

Worth confirming first whether the dashboard card actually renders the wrong venue when workshop_host is lost (follow the same repro sketch as #2975), or only shows no venue.