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

client/src/hooks/useExchangeRates.ts

@@ -2,7 +2,7 @@ import { useCallback, useEffect, useState } from 'react'
 
 /**
  * Live FX rates for the Costs panel, used to convert every amount into the user's
- * display currency. Fetches exchangerate-api.com (no key, already CSP-allowlisted
+ * display currency. Fetches api.frankfurter.dev (no key, already CSP-allowlisted
  * for the dashboard widget) for the given base and caches per base in memory +
  * localStorage for a few hours. rates[X] = units of X per 1 base, so an amount in
  * currency C converts to base as `amount / rates[C]`.
@@ -33,14 +33,19 @@ export function useExchangeRates(base: string) {
     if (cached) setRates(cached.rates)
     if (cached && Date.now() - cached.ts < TTL_MS) return
     let cancelled = false
-    fetch(`https://api.exchangerate-api.com/v4/latest/${encodeURIComponent(upper)}`)
+    fetch(`https://api.frankfurter.dev/v2/rates?base=${encodeURIComponent(upper)}`)
       .then(r => r.json())
-      .then((d: { rates?: Record<string, number> }) => {
-        if (cancelled || !d?.rates) return
-        const entry = { rates: d.rates, ts: Date.now() }
+      .then((d: Array<{ quote?: string; rate?: number }>) => {
+        if (cancelled || !Array.isArray(d)) return
+        // Frankfurter omits the base's own self-rate, so seed it with `base = 1`.
+        const rates: Record<string, number> = { [upper]: 1 }
+        for (const r of d) {
+          if (r && typeof r.quote === 'string' && typeof r.rate === 'number') rates[r.quote] = r.rate
+        }
+        const entry = { rates, ts: Date.now() }
         mem.set(upper, entry)
         try { localStorage.setItem('trek_fx_' + upper, JSON.stringify(entry)) } catch { /* ignore */ }
-        setRates(d.rates)
+        setRates(rates)
       })
       .catch(() => { /* offline → keep cached/identity */ })
     return () => { cancelled = true }

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])