SECONDS_PER_YEAR: 31556952n = 31_556_952n

Seconds per year used by the interest model = 365.2425 days × 86400 (the Gregorian year). Verified on the fork (Phase 4), NOT 365 (31_536_000) nor 365.25 (31_557_600). Fixed in the contract (no setter), so it is bundled. See docs/01-ground-truth.md §7.