Searching "Japan" now finds JPY, "Canada" finds CAD, etc. — matching
just the currency's own display name wasn't enough, since e.g.
"Canadian Dollar" doesn't contain "Canada" as a substring.
Adds a per-platform regionDisplayName(regionCode) (java.util.Locale
on JVM/Android, NSLocale on Apple, Intl.DisplayNames on web) and
reuses CurrencyFlag.kt's currency-to-country-code derivation (now
extracted as issuingCountryCodes) to look up the country/countries
behind a currency code. "EU" is hardcoded to "European Union" since
it's not a real ISO 3166-1 code platform locale data can resolve.
Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01FXcrACM5sok3M1KQJ8kByy
tyiuandClaude Sonnet 5
eafaeaa8d3