fix(spa): fallback font-serif to Prompt for Thai characters

apps/spa/src/App.tsx

@@ -1,4 +1,5 @@
 import { useEffect } from 'react'
+import { useTranslation } from 'react-i18next'
 import { BrowserRouter, Routes, Route } from 'react-router-dom'
 import ScrollToTop from './components/ScrollToTop'
 import { initLiff } from './lib/liff'
@@ -23,6 +24,8 @@ import ProfilePage from './pages/ProfilePage'
 import CartDrawer from './components/CartDrawer'
 
 function App() {
+  const { i18n } = useTranslation();
+
   useEffect(() => {
     const liffId = import.meta.env.VITE_LIFF_ID;
     if (liffId) {
@@ -32,6 +35,19 @@ function App() {
     }
   }, []);
 
+  useEffect(() => {
+    const lang = i18n.language;
+    document.body.classList.remove('font-sans-ja', 'font-sans-zh', 'font-sans-ko');
+    
+    if (lang === 'ja') {
+      document.body.classList.add('font-sans-ja');
+    } else if (lang === 'zh') {
+      document.body.classList.add('font-sans-zh');
+    } else if (lang === 'ko') {
+      document.body.classList.add('font-sans-ko');
+    }
+  }, [i18n.language]);
+
   return (
     <BrowserRouter>
       <ScrollToTop />