deals.currency has no DB CHECK (only accounts.default_currency does),
so legacy rows, imports, or hand-edited data can hold a structurally
invalid code (e.g. "United States"). Intl.NumberFormat throws a
RangeError on such codes, which would crash any deal-card / contact
render that passes deal.currency straight through.
Guard formatCurrency with a try/catch that falls back to "CODE 1,234"
so a bad value degrades gracefully instead of taking down the view.
Add currency.test.ts locking in the defaults, the no-throw contract,
and formatCurrencyShort's symbol/fallback behavior.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
