Exclude withdrawn currencies from the web currency list

Intl.supportedValuesOf('currency') includes several codes for
currencies that have actually been withdrawn/superseded — unlike
JVM/Android/Apple, which derive "currently used" from each ISO
country's live-assigned currency (java.util.Currency/NSLocale), the
web platform has no equivalent API, so this app was showing them
unfiltered.

Confirmed exactly which codes by diffing the web list against the
JVM's own live-derived set: ANG, CUC, HRK, SLL, and ZWL are genuinely
withdrawn/superseded national currencies, now excluded via a manually
maintained list (the web platform's only option here). XDR and XSU
were also missing from the JVM's set, but only because they aren't
tied to any ISO country — not because they're withdrawn — so those
stay, same reasoning this codebase already applies to precious
metals.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01FXcrACM5sok3M1KQJ8kByy

shared/src/webMain/kotlin/xyz/tyiu/satsprice/SystemCurrencies.web.kt

@@ -12,13 +12,28 @@ private fun jsCurrencyDisplayName(code: String): String = js(
     "(function() { var names = new Intl.DisplayNames(undefined, { type: 'currency' }); return names.of(code); })()",
 )
 
+/**
+ * `Intl.supportedValuesOf('currency')` includes a handful of codes for currencies that have
+ * actually been withdrawn/superseded since — unlike JVM/Android/Apple, there's no web API to
+ * derive "currently assigned to some country" the way `java.util.Currency`/`NSLocale` do (see
+ * [localeCurrencyCode] below), so this is a manually maintained exclusion list instead, checked
+ * (2026-09-10) against the JVM's own live-derived set. Needs a new entry whenever another
+ * currency is retired.
+ */
+private val WITHDRAWN_CURRENCY_CODES = setOf(
+    "ANG", // Netherlands Antillean Guilder — replaced by XCG (Caribbean Guilder), April 2025
+    "CUC", // Cuban Convertible Peso — unified into CUP, January 2021
+    "HRK", // Croatian Kuna — replaced by EUR, January 2023
+    "SLL", // Sierra Leonean Leone (old) — redenominated to SLE, 2022
+    "ZWL", // Zimbabwean Dollar (old) — replaced by ZWG (Zimbabwe Gold), April 2024
+)
+
 actual fun systemCurrencies(): List<CurrencyInfo> =
     jsSupportedCurrencyCodes()
         .toList()
-        .map { jsCode ->
+        .map { it.toString() }
-            val code = jsCode.toString()
+        .filterNot { it in WITHDRAWN_CURRENCY_CODES }
-            CurrencyInfo(code, jsCurrencyDisplayName(code))
+        .map { code -> CurrencyInfo(code, jsCurrencyDisplayName(code)) }
-        }
         .sortedBy { it.code }
 
 /**