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/components/ThreadCard.tsx

@@ -1,4 +1,5 @@
 import { useNavigate } from "@tanstack/react-router";
+import { useCurrency } from "../hooks/useCurrency";
 import { formatPrice } from "../lib/formatters";
 import { LucideIcon } from "../lib/iconData";
 
@@ -22,10 +23,11 @@ function formatDate(iso: string): string {
 function formatPriceRange(
 	min: number | null,
 	max: number | null,
+	currency: Parameters<typeof formatPrice>[1],
 ): string | null {
 	if (min == null && max == null) return null;
-	if (min === max) return formatPrice(min);
-	return `${formatPrice(min)} - ${formatPrice(max)}`;
+	if (min === max) return formatPrice(min, currency);
+	return `${formatPrice(min, currency)} - ${formatPrice(max, currency)}`;
 }
 
 export function ThreadCard({
@@ -40,9 +42,10 @@ export function ThreadCard({
 	categoryIcon,
 }: ThreadCardProps) {
 	const navigate = useNavigate();
+	const currency = useCurrency();
 
 	const isResolved = status === "resolved";
-	const priceRange = formatPriceRange(minPriceCents, maxPriceCents);
+	const priceRange = formatPriceRange(minPriceCents, maxPriceCents, currency);
 
 	return (
 		<button