feat: wire currency conversion into price display

useFormatters().price() now accepts an optional sourceCurrency param.
When showConversions is enabled and the source differs from the user's
currency, it converts via ECB rates and shows dual format:
"€200.00 (~$218.00)". ItemCard and CollectionView pass priceCurrency
through from API data. Setup detail items also pass priceCurrency.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

src/client/hooks/useFormatters.ts

@@ -1,15 +1,47 @@
-import { formatPrice, formatWeight } from "../lib/formatters";
+import {
+	type Currency,
+	formatDualPrice,
+	formatPrice,
+	formatWeight,
+} from "../lib/formatters";
 import { useCurrency } from "./useCurrency";
+import { convertClientPrice, useExchangeRates } from "./useExchangeRates";
 import { useLanguage } from "./useLanguage";
 import { useWeightUnit } from "./useWeightUnit";
 
 export function useFormatters() {
 	const unit = useWeightUnit();
-	const { currency } = useCurrency();
+	const { currency, showConversions } = useCurrency();
 	const locale = useLanguage();
+	const { data: ratesData } = useExchangeRates();
+	const rates = ratesData?.rates;
+
 	return {
 		weight: (grams: number | null) => formatWeight(grams, unit, locale),
-		price: (cents: number | null) => formatPrice(cents, currency, locale),
+		/**
+		 * Format a price. If sourceCurrency differs from user's currency and
+		 * showConversions is enabled, returns dual format: "€200.00 (~$218.00)".
+		 * Otherwise returns price in source currency (or user's currency if no source given).
+		 */
+		price: (
+			cents: number | null,
+			sourceCurrency?: Currency | string | null,
+		) => {
+			if (cents == null) return "--";
+			const source = (sourceCurrency as Currency) || currency;
+			if (showConversions && rates && source !== currency) {
+				const converted = convertClientPrice(cents, source, currency, rates);
+				const dual = formatDualPrice({
+					sourceCents: cents,
+					sourceCurrency: source as Currency,
+					targetCurrency: currency,
+					convertedCents: converted,
+					locale,
+				});
+				return `${dual.source} (${dual.converted})`;
+			}
+			return formatPrice(cents, source as Currency, locale);
+		},
 		unit,
 		currency,
 		locale,