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

server/api/public/bookings.post.ts

@@ -21,6 +21,7 @@ export default defineEventHandler(async (event): Promise<CreateBookingResponse>
     quantity?: number
     ticketType?: TicketType
     personInChargeId?: string
+    locale?: string | null
   }>(event)
 
   const input = parseCreateBookingInput(body)
@@ -42,6 +43,7 @@ export default defineEventHandler(async (event): Promise<CreateBookingResponse>
     eventId: bookingMode.eventId,
     customerName: input.customerName,
     customerPhone: input.customerPhone,
+    locale: input.locale,
     bookingModeId: bookingMode.id,
     bookingMode: bookingMode.value,
     quantity: input.quantity,