fix(miniapp): address review feedback

apps/miniapp/src/components/finance/member-balance-card.tsx

@@ -1,6 +1,7 @@
 import { For, Show } from 'solid-js'
 
 import { cn } from '../../lib/cn'
+import { majorStringToMinor, sumMajorStrings } from '../../lib/money'
 import type { MiniAppDashboard } from '../../miniapp-api'
 import { MiniChip, StatCard } from '../ui'
 
@@ -11,31 +12,6 @@ type Props = {
   detail?: boolean
 }
 
-function majorStringToMinor(value: string): bigint {
-  const trimmed = value.trim()
-  const negative = trimmed.startsWith('-')
-  const normalized = negative ? trimmed.slice(1) : trimmed
-  const [whole = '0', fraction = ''] = normalized.split('.')
-  const major = BigInt(whole || '0')
-  const cents = BigInt((fraction.padEnd(2, '0').slice(0, 2) || '00').replace(/\D/g, '') || '0')
-  const minor = major * 100n + cents
-
-  return negative ? -minor : minor
-}
-
-function minorToMajorString(value: bigint): string {
-  const negative = value < 0n
-  const absolute = negative ? -value : value
-  const whole = absolute / 100n
-  const fraction = String(absolute % 100n).padStart(2, '0')
-
-  return `${negative ? '-' : ''}${whole.toString()}.${fraction}`
-}
-
-function sumMajorStrings(left: string, right: string): string {
-  return minorToMajorString(majorStringToMinor(left) + majorStringToMinor(right))
-}
-
 export function MemberBalanceCard(props: Props) {
   const utilitiesAdjustedMajor = () =>
     sumMajorStrings(props.member.utilityShareMajor, props.member.purchaseOffsetMajor)