chore(web): extract formatUsd into shared lib/format module

apps/web/src/components/dashboard/DepositTab.tsx

@@ -1,15 +1,7 @@
 import { useTranslation } from "react-i18next";
 import { AmountInput } from "../ui/AmountInput";
 import type { ApiPosition, ApiVault } from "../../lib/api";
-
-function formatUsd(value: number, locale: string) {
-  return value.toLocaleString(locale === "fr" ? "fr-FR" : "en-US", {
-    style: "currency",
-    currency: "USD",
-    minimumFractionDigits: 2,
-    maximumFractionDigits: 2,
-  });
-}
+import { formatUsd } from "../../lib/format";
 
 interface DepositTabProps {
   amount: string;

apps/web/src/components/dashboard/PositionSummary.tsx

@@ -1,14 +1,6 @@
 import { useTranslation } from "react-i18next";
 import type { ApiPosition } from "../../lib/api";
-
-function formatUsd(value: number, locale: string) {
-  return value.toLocaleString(locale === "fr" ? "fr-FR" : "en-US", {
-    style: "currency",
-    currency: "USD",
-    minimumFractionDigits: 2,
-    maximumFractionDigits: 2,
-  });
-}
+import { formatUsd } from "../../lib/format";
 
 interface PositionSummaryProps {
   position: ApiPosition;

apps/web/src/lib/format.ts

@@ -0,0 +1,15 @@
+/**
+ * Formats a numeric USD value as a localised currency string.
+ *
+ * @param value  - The numeric amount to format.
+ * @param locale - The i18n locale string (e.g. "en", "fr").
+ * @returns A string such as "$1,234.56" or "1 234,56 $US".
+ */
+export function formatUsd(value: number, locale: string): string {
+  return value.toLocaleString(locale === "fr" ? "fr-FR" : "en-US", {
+    style: "currency",
+    currency: "USD",
+    minimumFractionDigits: 2,
+    maximumFractionDigits: 2,
+  });
+}