i18n: normalize language switch next URL to avoid double locale prefixes

mandelstudio/templates/oxyan/headers/partials/carbasa-user-bar.html

@@ -1,4 +1,4 @@
-{% load i18n %}
+{% load i18n i18n_helpers %}
 <style>
   .ms-lang-switcher { display: inline-flex; align-items: center; }
   .ms-lang-switcher .form-select {
@@ -28,7 +28,7 @@
     <a class="ms-lang-switcher-link" href="/language-test/" title="Language test">LANG</a>
     <form action="{% url 'set_language' %}" method="post" class="ms-lang-switcher me-2" aria-label="Language switcher">
         {% csrf_token %}
-        <input name="next" type="hidden" value="{{ request.get_full_path }}">
+        <input name="next" type="hidden" value="{{ request.path|untranslated_url }}">
         <label for="header-language-switcher" class="visually-hidden">{% trans "Language" %}</label>
         <select id="header-language-switcher" name="language" class="form-select form-select-sm" onchange="this.form.submit()">
             {% get_current_language as LANGUAGE_CODE %}