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)

app/pages/index.vue

@@ -1,7 +1,12 @@
 <script lang="ts" setup>
 import type { FormError, FormSubmitEvent } from '@nuxt/ui'
 
-import { isValidPhoneNumber, type PublicContact } from '~~/shared/auth'
+import {
+  DEFAULT_PHONE_COUNTRY_CODE,
+  isValidPhoneNumber,
+  normalizePhoneNumber,
+  type PublicContact
+} from '~~/shared/auth'
 import type { CreateBookingResponse } from '~~/shared/booking'
 import {
   BOOKING_MODE_OPTIONS,
@@ -51,7 +56,7 @@ const personInCharge = computed(() => {
 
 const form = reactive({
   name: '',
-  phone: '',
+  phone: DEFAULT_PHONE_COUNTRY_CODE,
   bookingMode: 'table' as BookingMode,
   quantity: 1,
   ticketType: 'vip' as TicketType
@@ -85,7 +90,7 @@ function validateBooking(state: typeof form): FormError[] {
   if (!state.phone.trim()) {
     errors.push({ name: 'phone', message: 'Please enter a contact number.' })
   } else if (!isValidPhoneNumber(state.phone.trim())) {
-    errors.push({ name: 'phone', message: 'Use a valid phone number with 8 to 15 digits.' })
+    errors.push({ name: 'phone', message: 'Use a valid phone number with country code, e.g. +60123456789.' })
   }
 
   if (state.quantity < 1) {
@@ -117,7 +122,7 @@ async function bookTicket(event: FormSubmitEvent<typeof form>) {
       method: 'POST',
       body: {
         customerName: form.name.trim(),
-        customerPhone: form.phone.trim(),
+        customerPhone: normalizePhoneNumber(form.phone),
         bookingMode: form.bookingMode,
         quantity: form.quantity,
         ticketType: form.ticketType,
@@ -181,7 +186,7 @@ async function bookTicket(event: FormSubmitEvent<typeof form>) {
             </UFormField>
 
             <UFormField name="phone" label="Phone Number" required>
-              <UInput v-model="form.phone" size="xl" type="tel" class="w-full" placeholder="e.g. 0123456789" />
+              <UInput v-model="form.phone" size="xl" type="tel" class="w-full" placeholder="e.g. +60123456789" />
             </UFormField>
           </div>