fix(i18n): Fix Chinese language issues and hyphenated locale persistence

- Fix missing Chinese translations in main-zh-CN.json and main-zh-TW.json
- Fix language selection not persisting for hyphenated locales (zh-CN, zh-TW, es-US, fr-CA, pt-BR)
- Update normalizeCurrentLanguage to check exact match before normalization

react/features/base/i18n/i18next.ts

@@ -80,7 +80,7 @@ const options: i18next.InitOptions = {
     interpolation: {
         escapeValue: false // not needed for react as it escapes by default
     },
-    load: 'languageOnly',
+    load: 'all',
     ns: [ 'main', 'languages', 'countries', 'translation-languages' ],
     react: {
         // re-render when a new resource bundle is added

react/features/settings/functions.any.ts

@@ -96,6 +96,11 @@ function normalizeCurrentLanguage(language: string) {
         return;
     }
 
+    // First check if the language code exists as-is (e.g., 'zh-CN', 'fr-CA')
+    if (LANGUAGES.includes(language)) {
+        return language;
+    }
+
     const [ country, lang ] = language.split('-');
     const jitsiNormalized = `${country}${lang ?? ''}`;