feat(annotation): 添加保存并跳转到下一段功能

- 新增 SAVE_AND_NEXT_LABEL 常量用于保存并跳转按钮文本
- 添加 saveDisabled 状态控制保存按钮禁用逻辑
- 修改顶部工具栏布局为三列网格结构
- 在工具栏中间位置添加保存并跳转到下一段/下一条按钮
- 调整保存按钮样式移除主色调设置
- 优化保存按钮禁用状态逻辑统一管理
- 修改保存功能区分普通保存和跳转保存操作

frontend/src/pages/DataAnnotation/Annotate/LabelStudioTextEditor.tsx

@@ -102,6 +102,7 @@ const NO_ANNOTATION_CONFIRM_TITLE = "没有标注任何内容";
 const NO_ANNOTATION_CONFIRM_OK_TEXT = "设为无标注并保存";
 const NOT_APPLICABLE_CONFIRM_TEXT = "设为不适用并保存";
 const NO_ANNOTATION_CONFIRM_CANCEL_TEXT = "继续标注";
+const SAVE_AND_NEXT_LABEL = "保存并跳转到下一段/下一条";
 
 type NormalizedTaskList = {
   items: EditorTaskListItem[];
@@ -1146,6 +1147,8 @@ export default function LabelStudioTextEditor() {
   }, [message, origin, saveFromExport]);
 
   const canLoadMore = taskTotalPages > 0 && taskPage + 1 < taskTotalPages;
+  const saveDisabled =
+    !iframeReady || !selectedFileId || saving || segmentSwitching || loadingTaskDetail;
   const loadMoreNode = canLoadMore ? (
     <div className="p-2 text-center">
       <Button
@@ -1209,7 +1212,7 @@ export default function LabelStudioTextEditor() {
   return (
     <div className="h-full flex flex-col">
       {/* 顶部工具栏 */}
-      <div className="flex items-center justify-between px-3 py-2 border-b border-gray-200 bg-white">
+      <div className="grid grid-cols-[1fr_auto_1fr] items-center px-3 py-2 border-b border-gray-200 bg-white">
         <div className="flex items-center gap-2">
           <Button icon={<LeftOutlined />} onClick={() => navigate("/data/annotation")}>
             返回
@@ -1223,7 +1226,18 @@ export default function LabelStudioTextEditor() {
             标注编辑器
           </Typography.Title>
         </div>
-        <div className="flex items-center gap-2">
+        <div className="flex items-center justify-center">
+          <Button
+            type="primary"
+            icon={<SaveOutlined />}
+            loading={saving}
+            disabled={saveDisabled}
+            onClick={() => requestExport(true)}
+          >
+            {SAVE_AND_NEXT_LABEL}
+          </Button>
+        </div>
+        <div className="flex items-center gap-2 justify-end">
           <Button
             icon={<ReloadOutlined />}
             loading={loadingTasks}
@@ -1232,11 +1246,10 @@ export default function LabelStudioTextEditor() {
             刷新
           </Button>
           <Button
-            type="primary"
             icon={<SaveOutlined />}
             loading={saving}
-            disabled={!iframeReady || !selectedFileId}
-            onClick={() => requestExport(true)}
+            disabled={saveDisabled}
+            onClick={() => requestExport(false)}
           >
             保存
           </Button>