chore: validate prices and tick sizes

[suhaiIkakar]

compare price/tick bounds with Big instead of parseFloat to avoid floating-point edge cases in priceValid and
isTickSizeSmaller.

---

Note

Medium Risk
Changes core order validation comparisons to use big-integer arithmetic instead of parseFloat, which can alter boundary behavior for prices/tick sizes and impact order submission in edge cases.

Overview
Updates tick/price validation to avoid floating-point edge cases by switching isTickSizeSmaller and priceValid from parseFloat-based comparisons to mjs-biginteger (Big) comparisons, including computing the upper bound as 1 - tickSize with arbitrary-precision math.

Adds mjs-biginteger as a runtime dependency to support these comparisons.

^{Reviewed by Cursor Bugbot for commit 1f53d4c. Bugbot is set up for automated code reviews on this repo. Configure here.}