feat: send ticket receipts via WhatsApp and normalize phone numbers

Add WhatsApp API integration for automated receipt delivery
Enforce country codes for all phone number inputs (defaults to +60)

server/api/public/bookings.post.ts

@@ -7,6 +7,7 @@ import { createBooking } from '../../utils/booking-repository'
 import { buildBookingMessage, parseCreateBookingInput } from '../../utils/bookings'
 import { assertBadRequest } from '../../utils/http'
 import { getPublicContactById } from '../../utils/user-repository'
+import { buildWhatsAppDeepLink } from '../../utils/whatsapp'
 
 export default defineEventHandler(async (event): Promise<CreateBookingResponse> => {
   const body = await readBody<{
@@ -46,7 +47,7 @@ export default defineEventHandler(async (event): Promise<CreateBookingResponse>
 
   const confirmationUrl = buildAppUrl(event, `/confirmation/${confirmationToken}`)
   const whatsappMessage = buildBookingMessage(booking, confirmationUrl)
-  const whatsappUrl = `https://wa.me/${booking.personInChargePhoneNumber}?text=${encodeURIComponent(whatsappMessage)}`
+  const whatsappUrl = buildWhatsAppDeepLink(booking.personInChargePhoneNumber, whatsappMessage)
 
   return {
     booking,