chore: move to Frankfurter API for exchange rate (#1214)

client/src/pages/DashboardPage.test.tsx

@@ -20,8 +20,11 @@ beforeEach(() => {
   } as any);
   // Intercept CurrencyWidget's external fetch so it resolves before teardown
   server.use(
-    http.get('https://api.exchangerate-api.com/v4/latest/:currency', () => {
-      return HttpResponse.json({ rates: { USD: 1.08, EUR: 1, CHF: 0.97 } });
+    http.get('https://api.frankfurter.dev/v2/rates', () => {
+      return HttpResponse.json([
+        { date: '2026-06-16', base: 'EUR', quote: 'USD', rate: 1.08 },
+        { date: '2026-06-16', base: 'EUR', quote: 'CHF', rate: 0.97 },
+      ]);
     }),
   );
 });

client/src/pages/DashboardPage.tsx

@@ -461,9 +461,15 @@ function CurrencyTool(): React.ReactElement {
   const [rates, setRates] = useState<Record<string, number> | null>(null)
 
   const fetchRate = React.useCallback(() => {
-    fetch(`https://api.exchangerate-api.com/v4/latest/${from}`)
+    fetch(`https://api.frankfurter.dev/v2/rates?base=${from}`)
       .then(r => r.json())
-      .then(d => setRates(d.rates ?? null))
+      .then((d: Array<{ quote: string; rate: number }>) => {
+        if (!Array.isArray(d)) { setRates(null); return }
+        // Frankfurter omits the base's own self-rate; seed it so `from` stays selectable.
+        const map: Record<string, number> = { [from]: 1 }
+        for (const r of d) map[r.quote] = r.rate
+        setRates(map)
+      })
       .catch(() => setRates(null))
   }, [from])