feat(i18n): display only active language in translation fields

Update TranslationFields to render a single input for the current locale
Ensure entity base names fallback to the active locale translation on save

frontend/src/views/ItemEdit.vue

@@ -11,7 +11,7 @@ import { api, type ConfigType, type ItemPayload, type Language, type Options, ty
 
 const route = useRoute();
 const router = useRouter();
-const { t } = useI18n();
+const { locale, t } = useI18n();
 const options = ref<Options | null>(null);
 const languages = ref<Language[]>([]);
 const loading = ref(true);
@@ -53,6 +53,15 @@ function closeEditor() {
   void router.push(cancelTo.value);
 }
 
+function itemNameForSave() {
+  const baseName = itemForm.value.name.trim();
+  if (baseName !== '') {
+    return itemForm.value.name;
+  }
+
+  return itemForm.value.translations[String(locale.value || '')]?.name ?? '';
+}
+
 async function loadOptions() {
   const [loadedOptions, loadedLanguages] = await Promise.all([api.options(), api.languages()]);
   options.value = loadedOptions;
@@ -131,7 +140,7 @@ async function saveItem() {
 
   try {
     const payload: ItemPayload = {
-      name: itemForm.value.name,
+      name: itemNameForSave(),
       translations: itemForm.value.translations,
       categoryId: Number(itemForm.value.categoryId),
       usageId: itemForm.value.usageId ? Number(itemForm.value.usageId) : null,