fix(settings): keep the language and save settings one after the other

src/i18n.js

@@ -1,12 +1,13 @@
 import i18n from 'i18next';
 import {initReactI18next} from 'react-i18next';
 import HttpBackend from 'i18next-http-backend';
+import {cacheLanguage, readCachedLanguage} from './utils/settings.js';
 
 
 i18n.use(HttpBackend)
     .use(initReactI18next)
     .init({
-        lng: 'de',
+        lng: readCachedLanguage() ?? 'de',
         fallbackLng: 'en',
         backend: {
             // A browser kept an old file without its Cache-Control and showed raw keys; a new URL per version avoids that.
@@ -17,4 +18,6 @@ i18n.use(HttpBackend)
         }
     });
 
+i18n.on('languageChanged', cacheLanguage);
+
 export default i18n;