fix(notebook): 来源搜索导入后立刻显示占位卡并刷新来源列表

- handleImport 成功后调用 onUploadComplete 通知父组件（原先缺失）并关闭弹窗
- 新增 pendingImportTitles state，同步导入后立刻渲染 PendingSourceCard
- sources 刷新后按标题匹配移除占位卡并自动选中新来源

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

frontend-web/src/components/assistant-ui/document-upload-popup.tsx

@@ -405,8 +405,15 @@ const DocumentUploadPopupContent: FC<{
       if (response.ok) {
         const data = await response.json() as { imported_count?: number };
         toast.success(`成功导入 ${data.imported_count || dataList.length} 个来源`);
-        setListData([]);
-        handleBatchDelete();
+        onUploadComplete?.(
+          selectedSearchSources.map((s) => ({
+            id: undefined,
+            title: s.title,
+            task_id: undefined,
+            status: "success" as const,
+          }))
+        );
+        onOpenChange(false);
       } else {
         const errorData = await response.json() as { detail?: string };
         toast.error(errorData.detail || "导入失败，请重试");