Pull the last 30 days of real traffic from Vercel into world_audience_cache, so GET /api/world/audience never has to.

Also runs as part of /api/cron/daily-scrape; this exists so the figure can be refreshed on its own schedule (or by hand after wiring the token up) without kicking off a scrape.

Returns {"configured": false} and changes nothing when VERCEL_ANALYTICS_TOKEN is unset — the numbers stay null rather than becoming a placeholder. {"refreshed": false} means the fetch failed and the previous, real, cached row was deliberately left in place.