From eb1bb8aeec419ee518ed0ca93fac1c736c74573d Mon Sep 17 00:00:00 2001
From: Jean-Luc Makiola <business@jeanlucmakiola.de>
Date: Thu, 12 Mar 2026 09:23:46 +0100
Subject: [PATCH] feat(04-01): add locale parameter to formatCurrency, default
 'en'

- Replace hardcoded 'de-DE' with optional locale parameter defaulting to 'en'
- Defensive locale || 'en' guard prevents RangeError on empty string
- All existing call sites get English formatting (FIX-01)
- Third arg enables locale-aware chart tooltips in follow-on plans
---
 frontend/src/lib/format.ts | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/frontend/src/lib/format.ts b/frontend/src/lib/format.ts
index 4c5ecf7..90592be 100644
--- a/frontend/src/lib/format.ts
+++ b/frontend/src/lib/format.ts
@@ -1,5 +1,9 @@
-export function formatCurrency(amount: number, currency: string = 'EUR'): string {
-  return new Intl.NumberFormat('de-DE', {
+export function formatCurrency(
+  amount: number,
+  currency: string = 'EUR',
+  locale: string = 'en'
+): string {
+  return new Intl.NumberFormat(locale || 'en', {
     style: 'currency',
     currency,
   }).format(amount)