fix(import): show conversion guidance for batch failures

Show one localized conversion guide in the batch result when any failed file has an unrecognized format. Batch errors are stored separately from the single-file error state, so they previously missed the guidance.

src/components/import/ImportArea.vue

@@ -99,6 +99,9 @@ function showImportOutcome(result: ImportResult) {
 
 const importError = ref<string | null>(null)
 const isUnrecognizedFormat = computed(() => importError.value === 'error.unrecognized_format')
+const hasUnrecognizedBatchFormat = computed(() =>
+  batchImportResult.value?.files.some((file) => file.status === 'failed' && file.error === 'error.unrecognized_format')
+)
 const hasImportLog = ref(false)
 const importDiagnostics = ref<{
   logFile: string | null
@@ -1075,6 +1078,21 @@ const getMergeFileProgressText = (file: MergeFileInfo) =>
           </template>
         </FileListItem>
       </div>
+      <div v-if="hasUnrecognizedBatchFormat" class="mt-4 space-y-2">
+        <p class="text-xs leading-relaxed text-gray-500 dark:text-gray-400">
+          {{ t('home.import.errors.unrecognizedFormatHint') }}
+        </p>
+        <UButton
+          :href="conversionGuideUrl"
+          target="_blank"
+          rel="noopener noreferrer"
+          size="xs"
+          variant="soft"
+          icon="i-heroicons-arrow-top-right-on-square"
+        >
+          {{ t('home.import.viewConversionGuide') }}
+        </UButton>
+      </div>
     </div>
 
     <!-- 默认导入区域（非批量状态） -->