feat: 实现文件夹递归扫描功能

- 启用文件夹选择时的递归扫描，遍历所有子文件夹
- 添加递归扫描选项复选框，用户可以选择是否扫描子文件夹
- 动态更新按钮文本显示当前扫描模式
- 改进扫描状态反馈，显示扫描进度和结果统计
- 添加状态显示区域，实时显示扫描状态和结果
- 优化用户体验，提供清晰的视觉反馈

现在用户可以：
- 选择文件夹时自动扫描所有子文件夹中的视频文件
- 通过复选框控制是否递归扫描
- 查看扫描进度和结果统计信息

apps/desktop/src/pages/tools/FrameExtractorTool.tsx

@@ -55,6 +55,7 @@ const FrameExtractorTool: React.FC = () => {
   const [ffmpegAvailable, setFfmpegAvailable] = useState<boolean | null>(null);
   const [selectedVideoForPreview, setSelectedVideoForPreview] = useState<VideoFileInfo | null>(null);
   const [currentPlayTime, setCurrentPlayTime] = useState<number>(0);
+  const [recursiveScan, setRecursiveScan] = useState<boolean>(true);
 
   // 检查 FFmpeg 可用性
   useEffect(() => {
@@ -107,7 +108,7 @@ const FrameExtractorTool: React.FC = () => {
 
       if (selected && typeof selected === 'string') {
         setSelectedFolder(selected);
-        await scanVideoFiles(selected, false);
+        await scanVideoFiles(selected, recursiveScan);
       }
     } catch (error) {
       console.error('选择文件夹失败:', error);
@@ -117,6 +118,8 @@ const FrameExtractorTool: React.FC = () => {
   // 扫描视频文件
   const scanVideoFiles = useCallback(async (folderPath: string, recursive: boolean) => {
     setIsScanning(true);
+    setCurrentFile(`正在扫描文件夹: ${folderPath}${recursive ? ' (递归)' : ''}`);
+
     try {
       const files = await invoke<VideoFileInfo[]>('scan_video_files', {
         request: {
@@ -125,10 +128,29 @@ const FrameExtractorTool: React.FC = () => {
           supported_formats: SUPPORTED_VIDEO_FORMATS,
         }
       });
-      
-      setSelectedVideos(files.filter(f => f.is_valid));
+
+      const validFiles = files.filter(f => f.is_valid);
+      setSelectedVideos(validFiles);
+
+      // 显示扫描结果
+      const totalFiles = files.length;
+      const validCount = validFiles.length;
+      const invalidCount = totalFiles - validCount;
+
+      console.log(`扫描完成: 找到 ${totalFiles} 个文件，其中 ${validCount} 个有效，${invalidCount} 个无效`);
+      setCurrentFile(`扫描完成: 找到 ${validCount} 个有效视频文件`);
+
+      // 2秒后清除状态信息
+      setTimeout(() => {
+        setCurrentFile('');
+      }, 2000);
+
     } catch (error) {
       console.error('扫描视频文件失败:', error);
+      setCurrentFile('扫描失败，请重试');
+      setTimeout(() => {
+        setCurrentFile('');
+      }, 3000);
     } finally {
       setIsScanning(false);
     }
@@ -266,9 +288,10 @@ const FrameExtractorTool: React.FC = () => {
             onClick={handleSelectFolder}
             disabled={isScanning || isExtracting}
             className="flex items-center gap-2 px-4 py-2 bg-green-500 text-white rounded-lg hover:bg-green-600 disabled:opacity-50 disabled:cursor-not-allowed transition-colors"
+            title={recursiveScan ? "选择文件夹并递归扫描所有子文件夹中的视频文件" : "选择文件夹并扫描其中的视频文件"}
           >
             <FolderOpen className="w-4 h-4" />
-            选择文件夹
+            选择文件夹{recursiveScan ? ' (递归)' : ''}
           </button>
 
           <button
@@ -279,6 +302,19 @@ const FrameExtractorTool: React.FC = () => {
             <Trash2 className="w-4 h-4" />
             清除选择
           </button>
+
+          {/* 递归扫描选项 */}
+          <div className="flex items-center gap-2 ml-4 pl-4 border-l border-gray-200">
+            <label className="flex items-center gap-2 text-sm text-gray-700 cursor-pointer">
+              <input
+                type="checkbox"
+                checked={recursiveScan}
+                onChange={(e) => setRecursiveScan(e.target.checked)}
+                className="rounded border-gray-300 text-blue-600 focus:ring-blue-500"
+              />
+              <span>递归扫描子文件夹</span>
+            </label>
+          </div>
         </div>
 
         <div className="flex items-center gap-3">
@@ -306,6 +342,18 @@ const FrameExtractorTool: React.FC = () => {
         </div>
       </div>
 
+      {/* 状态显示区域 */}
+      {(isScanning || currentFile) && (
+        <div className="bg-blue-50 border border-blue-200 rounded-lg p-3">
+          <div className="flex items-center gap-2">
+            {isScanning && <RefreshCw className="w-4 h-4 text-blue-600 animate-spin" />}
+            <span className="text-sm text-blue-800">
+              {currentFile || '正在处理...'}
+            </span>
+          </div>
+        </div>
+      )}
+
       {/* 视图切换 */}
       <div className="flex items-center gap-2 bg-white rounded-lg p-1 shadow-sm border w-fit">
         <button