art-35-tempo-payments-business-case 2026-06-19 xbrli:pure iso4217:USD MIGRATE railswift stablecoinusdc per_tx_incumbent_usd43 per_tx_tempo_usd0.0003 per_tx_saving_usd42.9997 saving_bps17.2 monthly_saving_usd34399.76 412797.12 impl_cost_usd45000 break_even_months1.3