Fix Live Preview 404 for the two new tracking email templates

order-tracking-added/order-tracking-corrected were missing from
VALID_TYPES (app/email-preview/[type]/page.tsx), EmailTemplateType
(app/lib/payload.ts), and ORDER_STATUS_EMAIL_ICON (emailTemplates.ts)
— Live Preview 404'd for both since they were added to the Payload
collection without a matching frontend update.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

app/lib/emailTemplates.ts

@@ -313,6 +313,8 @@ export const ORDER_STATUS_EMAIL_ICON: Record<string, string> = {
   "order-cancelled": "✕",
   "order-return-requested": "↩",
   "order-returned": "✓",
+  "order-tracking-added": "📦",
+  "order-tracking-corrected": "📦",
 };
 
 export function renderOrderStatusHtml(