feat(i18n): add multi-language support (en/zh) across app and server

Implement useLocale composable and shared translation dictionaries
Translate public pages, booking flow, and receipt views
Store booking locale to send localized WhatsApp notifications

shared/booking.ts

@@ -1,3 +1,5 @@
+import type { AppLocale } from './i18n'
+
 export type BookingMode = string
 export type TicketType = string
 export type BookingStatus = 'pending' | 'confirmed'
@@ -41,6 +43,7 @@ export interface PublicBooking {
   event: DinnerEvent
   customerName: string
   customerPhone: string
+  locale: AppLocale
   bookingModeId: string | null
   bookingMode: BookingMode
   bookingModeLabel: string
@@ -68,6 +71,7 @@ export interface ReceiptBooking {
   event: DinnerEvent
   customerName: string
   customerPhone: string
+  locale: AppLocale
   bookingModeId: string | null
   bookingMode: BookingMode
   bookingModeLabel: string
@@ -158,11 +162,15 @@ export function isBookingStatus(value: string | null | undefined): value is Book
   return value === 'pending' || value === 'confirmed'
 }
 
-export function getBookingStatusLabel(value: BookingStatus | string, label?: string | null) {
-  if (label) {
+export function getBookingStatusLabel(value: BookingStatus | string, label?: string | null, locale: AppLocale = 'en') {
+  if (label && locale !== 'zh') {
     return label
   }
 
+  if (locale === 'zh') {
+    return value === 'confirmed' ? '已确认' : '等待负责人确认'
+  }
+
   return value === 'confirmed' ? 'Confirmed' : 'Pending PIC confirmation'
 }
 
@@ -178,8 +186,8 @@ export function getBookingTicketLabel(booking: Pick<PublicBooking | ReceiptBooki
   return booking.ticketLabel || booking.ticketType.toUpperCase()
 }
 
-export function formatBookingCurrency(value: number) {
-  return new Intl.NumberFormat('en-MY', {
+export function formatBookingCurrency(value: number, locale: AppLocale = 'en') {
+  return new Intl.NumberFormat(locale === 'zh' ? 'zh-MY' : 'en-MY', {
     style: 'currency',
     currency: 'MYR',
     minimumFractionDigits: 0,
@@ -187,8 +195,8 @@ export function formatBookingCurrency(value: number) {
   }).format(value)
 }
 
-export function getSeatLabel(seatNumber: number) {
-  return `Seat ${seatNumber}`
+export function getSeatLabel(seatNumber: number, locale: AppLocale = 'en') {
+  return locale === 'zh' ? `座位 ${seatNumber}` : `Seat ${seatNumber}`
 }
 
 export function calculateBookingInventorySummary(