Locale-aware currency formatting and symbol lookup for any ISO 4217 currency. Formats numbers as currency strings (e.g. 1234.56 USD → '$1,234.56', EUR in German locale → '1.234,56 €'), returns currency symbol, decimal separator, grouping separator, and currency name. Pure computation — no API key, no upstream latency. Supports 150+ currencies and custom locale overrides. Use for: financial report generation, invoice display, DeFi amount formatting, cross-regional price display.