feat: redesign weight summary legend and add currency selector

Redesign WeightSummaryCard stats from a disconnected 4-column grid to a
compact legend-style list with color dots, percentages, and a divider
before the total row. Switch chart and legend colors to a neutral gray
palette.

Add a currency selector to settings (USD, EUR, GBP, JPY, CAD, AUD) that
changes the displayed symbol across the app. This is visual only — no
value conversion is performed.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

src/client/lib/formatters.ts

@@ -21,7 +21,25 @@ export function formatWeight(
 	}
 }
 
-export function formatPrice(cents: number | null | undefined): string {
+export type Currency = "USD" | "EUR" | "GBP" | "JPY" | "CAD" | "AUD";
+
+const CURRENCY_SYMBOLS: Record<Currency, string> = {
+	USD: "$",
+	EUR: "€",
+	GBP: "£",
+	JPY: "¥",
+	CAD: "CA$",
+	AUD: "A$",
+};
+
+export function formatPrice(
+	cents: number | null | undefined,
+	currency: Currency = "USD",
+): string {
 	if (cents == null) return "--";
-	return `$${(cents / 100).toFixed(2)}`;
+	const symbol = CURRENCY_SYMBOLS[currency];
+	if (currency === "JPY") {
+		return `${symbol}${Math.round(cents / 100)}`;
+	}
+	return `${symbol}${(cents / 100).toFixed(2)}`;
 }