Add timeZone configuration to next-intl

- Add timeZone='Europe/Madrid' to NextIntlClientProvider
- Fixes ENVIRONMENT_FALLBACK warning about missing timeZone configuration
- Ensures consistent timezone handling across SSR and client rendering

frontend/app/components/IntlProvider.tsx

@@ -69,7 +69,7 @@ export function IntlProvider({ children }: IntlProviderProps) {
   }, [locale]);
 
   return (
-    <NextIntlClientProvider locale={locale} messages={localeMessages}>
+    <NextIntlClientProvider locale={locale} messages={localeMessages} timeZone="Europe/Madrid">
       {children}
     </NextIntlClientProvider>
   );