fix(web): guard price axis fraction digits

[ayaanoncrypto]

Fixes #8054

Summary

The price-axis formatter passed unvalidated decimals values into both minimumFractionDigits and maximumFractionDigits. A malformed or out-of-range precision value causes Intl.NumberFormat to throw RangeError: maximumFractionDigits value is out of range.

This change validates that the precision is an integer from 0 through the Intl-supported maximum of 100. Invalid values use the existing standard fiat formatter instead of constructing an invalid formatter. Regression coverage verifies valid fixed-precision formatting and the fallback path for precision above the limit.

Testing

• node /tmp/uniswap-8054-intl-smoke.js
• • git show --check HEAD
• • The focused Vitest command could not run in the sandbox because the repository dependency tree was unavailable and package installation stopped with ERR_PNPM_ENOSPC. CI should run the full repository checks.