Add frontend tests for localized currency and amount formatting

[mimijuwonlo-commits]

Area

Frontend i18n

Problem

Payment amounts must be readable and consistent across locales. Formatting tests should protect decimals, separators, and currency labels.

Acceptance Criteria

• Test NGN and supported token amount formatting
• Cover English and French locale output
• Handle tiny, zero, and large values
• Avoid rounding surprises in displayed payout amounts

Validation

Run frontend formatting and i18n tests.