fix: opt out of browser auto-translation

The app ships its own 7-language i18n and serves localized content, but mobile
browsers (Google Translate) were auto-translating the Chinese UI into broken
English (brand, nav, language dropdown). Add translate="no" + the Google
notranslate meta, and keep the attribute set on language changes.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

src/components/DocumentMeta.tsx

@@ -153,6 +153,8 @@ export function DocumentMeta() {
     const canonical = `${window.location.origin}${pathname}${search}`;
 
     document.documentElement.lang = lang;
+    // Keep browser auto-translation off — the app is already fully localized.
+    document.documentElement.setAttribute("translate", "no");
     document.title = title;
 
     setMeta('meta[name="description"]', "name", "description").content =