## Summary
- Fixes intermittent missing thousands separator on the dashboard
account card balance display, reproducible with Binance accounts whose
crypto-derived balances land on specific cent values.
- Root cause: `AmountDisplay` was doing `amountInCents / 100` → state →
`amount * 100` back into `formatCurrency`. This IEEE 754 round-trip
introduces floating-point noise (e.g. `1234567 / 100 * 100 =
1234566.9999...`), causing `Intl.NumberFormat` to produce unexpected
output.
- Fix: pass `amountInCents` directly to `formatCurrency` (which already
handles the `/100` division internally). The encryption fake-amount
display is also simplified from `useState + useEffect` to a single
`useMemo`.
## Changes
- `resources/js/components/ui/amount-display.tsx` — remove intermediate
`amount` state, pass `amountInCents` directly to `formatCurrency`
- `resources/js/utils/currency.test.ts` — new test file covering correct
formatting, thousands separators, and the specific float round-trip edge
cases
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