refactor: abstract site URL across email templates

- Add NEXT_PUBLIC_SITE_URL to .env.local
- Update email templates to accept siteUrl prop
- Update webhook handler to pass siteUrl from env var
- Update create-webhooks.graphql with placeholder URL

src/emails/OrderShipped.tsx

@@ -16,6 +16,7 @@ interface OrderShippedProps {
   items: OrderItem[];
   trackingNumber?: string;
   trackingUrl?: string;
+  siteUrl: string;
 }
 
 const translations: Record<
@@ -80,11 +81,12 @@ export function OrderShipped({
   items,
   trackingNumber,
   trackingUrl,
+  siteUrl,
 }: OrderShippedProps) {
   const t = translations[language] || translations.en;
 
   return (
-    <BaseLayout previewText={t.preview} language={language}>
+    <BaseLayout previewText={t.preview} language={language} siteUrl={siteUrl}>
       <Text style={styles.title}>{t.title}</Text>
       <Text style={styles.greeting}>{t.greeting.replace("{name}", customerName)}</Text>
       <Text style={styles.text}>{t.orderShipped}</Text>