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/payload.ts

@@ -817,7 +817,9 @@ export type EmailTemplateType =
   | "order-shipped"
   | "order-cancelled"
   | "order-return-requested"
-  | "order-returned";
+  | "order-returned"
+  | "order-tracking-added"
+  | "order-tracking-corrected";
 
 type PayloadEmailTemplate = {
   type: EmailTemplateType;