Build a small `capacity_calc(rps, bytes_per_req, peak_multiplier)` that returns peak bandwidth as GB/day: ``` peak_bandwidth_gb_per_day = (rps * peak_multiplier * bytes_per_req * 86400) / 1_000_000_000 ``` Round DOWN to an integer (ops dashboards always show whole GB). The harness prints results for: - realistic (10k RPS, 2KB payload, 3× peak) - edge (0 RPS — pre-launch) - huge scale (100k RPS, 50KB payload, 5× peak)