feat(annotation): 添加Label Studio文本编辑器的焦点管理功能

- 实现focusIframe函数用于聚焦iframe元素
- 在iframeReady和lsReady状态变化时自动聚焦编辑器
- 添加窗口聚焦事件监听器以保持编辑器焦点
- 在编辑器容器上添加鼠标点击事件以获取焦点
- 确保标签工作室准备就绪后正确设置焦点
- 优化用户体验通过自动焦点切换机制

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

@@ -172,6 +172,13 @@ export default function LabelStudioTextEditor() {
   const [segments, setSegments] = useState<SegmentInfo[]>([]);
   const [currentSegmentIndex, setCurrentSegmentIndex] = useState(0);
 
+  const focusIframe = useCallback(() => {
+    const iframe = iframeRef.current;
+    if (!iframe) return;
+    iframe.focus();
+    iframe.contentWindow?.focus?.();
+  }, []);
+
   const postToIframe = useCallback((type: string, payload?: unknown) => {
     const win = iframeRef.current?.contentWindow;
     if (!win) return;
@@ -600,6 +607,25 @@ export default function LabelStudioTextEditor() {
     initEditorForFile(selectedFileId);
   }, [selectedFileId, iframeReady, initEditorForFile]);
 
+  useEffect(() => {
+    if (!iframeReady) return;
+    focusIframe();
+  }, [focusIframe, iframeReady]);
+
+  useEffect(() => {
+    if (!lsReady) return;
+    focusIframe();
+  }, [focusIframe, lsReady]);
+
+  useEffect(() => {
+    if (!lsReady) return;
+    const handleWindowFocus = () => {
+      focusIframe();
+    };
+    window.addEventListener("focus", handleWindowFocus);
+    return () => window.removeEventListener("focus", handleWindowFocus);
+  }, [focusIframe, lsReady]);
+
   const segmentTreeData = useMemo(() => {
     if (!segmented || segments.length === 0) return [];
     const lineMap = new Map<number, SegmentInfo[]>();
@@ -870,7 +896,7 @@ export default function LabelStudioTextEditor() {
         {/* 右侧编辑器 - Label Studio iframe */}
         <div className="flex-1 flex flex-col min-h-0">
           {/* 编辑器区域 */}
-          <div className="flex-1 relative">
+          <div className="flex-1 relative" onMouseDown={focusIframe}>
             {(!iframeReady || loadingTaskDetail || (selectedFileId && !lsReady)) && (
               <div className="absolute inset-0 z-10 flex items-center justify-center bg-white/80">
                 <Spin