Throw error for invalid currency conversion inputs

[pavankumar-vh]

Overview

Fix currency conversion functions in common/src/util/currency.ts to throw errors instead of silently returning 0 for invalid inputs.

Bug Description

The previous version silently returned 0 when:

• centsPerCredit was 0 or negative (division by zero or negative rate)
• credits or amountInCents was NaN or Infinity

This is dangerous in money-conversion paths because misconfigurations would silently produce wrong values rather than failing loudly. A bad Stripe price setup or calculation error would result in users getting 0 credits/cents without any indication that something went wrong.

Fix

Changed to throw explicit errors with descriptive messages so invalid inputs are caught immediately during development and testing:

if (!(centsPerCredit > 0)) {
  throw new Error(
    `convertCreditsToUsdCents: centsPerCredit must be positive, got ${centsPerCredit}`,
  )
}
if (!Number.isFinite(credits)) {
  throw new Error(
    `convertCreditsToUsdCents: credits must be finite, got ${credits}`,
  )
}

Testing

No existing tests for these functions, but the fix prevents silent failures in production.

Files Changed

• common/src/util/currency.ts - Throw errors for invalid inputs

Scope

This change only touches common/ which is an approved contribution area per the Contributing Guide.