Refactored locale determination logic to directly use the language parameter from the environment, improving clarity and consistency in locale handling.

src/app.cpp

@@ -134,7 +134,7 @@ Wt::WLocale App::determineLocaleFromBrowser() const {
 
     // 1. Expliziter URL-Parameter ?lang=... hat Vorrang (z.B. de, de-DE, en, en-US, fr, es, it, tl, ja, zh, th)
     if (const auto *langParam = env_.getParameter("lang")) {
-        auto localeName = mapLanguageTag(langParam->toUTF8());
+        auto localeName = mapLanguageTag(*langParam);
         if (!localeName.empty()) {
             return makeLocale(localeName);
         }