Owner traffic overview, operator-filtered (session + owner allowlist)

Session-authenticated and restricted to OWNER_EMAILS. 503 when that variable is unset; 404, never 403, for any other caller. Inspections are reported as two series, external and operator; page views cannot be filtered at all (views.filterable: false) because the counter records only a day, a path, the link's own utm campaign tag, and a count.