feat: add currency to accounts

internal/misc/currency/currency.go

@@ -0,0 +1,51 @@
+// Package currency provides ISO 4217 currency code validation and a small
+// curated list of supported codes for UI selection.
+package currency
+
+import "strings"
+
+const Default = "CAD"
+
+// supported is the curated list of ISO 4217 codes shown in the account creation
+// UI. Add codes here as users request them. Validation accepts any 3-letter
+// uppercase code in this list.
+var supported = []string{
+	"CAD",
+	"USD",
+	"EUR",
+	"GBP",
+	"JPY",
+	"AUD",
+	"CHF",
+	"CNY",
+	"HKD",
+	"MXN",
+	"NZD",
+	"SGD",
+	"INR",
+	"BRL",
+	"KRW",
+	"TWD",
+}
+
+func Supported() []string {
+	out := make([]string, len(supported))
+	copy(out, supported)
+	return out
+}
+
+// Normalize uppercases and trims the input. It does not validate.
+func Normalize(code string) string {
+	return strings.ToUpper(strings.TrimSpace(code))
+}
+
+// IsValid reports whether code is a supported ISO 4217 code (case-insensitive).
+func IsValid(code string) bool {
+	c := Normalize(code)
+	for _, s := range supported {
+		if s == c {
+			return true
+		}
+	}
+	return false
+}