Add close/resolve-via-API support endpoint

Fleet sibling of MARS-399 (brainstorm bs-mr6rd8thu8f). Today PLUTO-444 ships only the REPLY leg (POST /api/internal/support-reply → staff comment + email; no status change). Closing a ticket (status→resuelto/cerrado) is /admin UI only. Add a bearer-gated resolve endpoint (or a status param) so an agent can close a ticket programmatically, same auth model (INTERNAL_EMAIL_KEY + server-side Soporte actor + setArchiveContext). Invariant: never resuelto until fix verified.