fix(meeting): 优化文件处理逻辑以避免内存溢出

修改文件选择逻辑，使用文件路径而非字节数据来处理音频文件
新增流式复制文件方法，分块处理大文件避免内存问题
移除旧的_saveFile方法，替换为更高效的_copyFileToLocal

lib/modules/meeting/controllers/meeting_home_controller.dart

@@ -340,7 +340,9 @@ class MeetingHomeController extends GetxController {
       fileName = path.basename(filePath);
     } else {
       FilePickerResult? result = await FilePicker.platform.pickFiles(
-        withData: true,
+        withData: false,
+        type: FileType.audio,
+        allowMultiple: false,
       );
       if (result != null) {
         PlatformFile file = result.files.first;
@@ -357,7 +359,8 @@ class MeetingHomeController extends GetxController {
           return;
         }
 
-        filePath = await _saveFile(file);
+        // 使用文件路径而不是字节数据
+        filePath = file.path ?? await _copyFileToLocal(file);
         fileName = file.name;
       } else {
         EasyLoading.dismiss();
@@ -419,6 +422,48 @@ class MeetingHomeController extends GetxController {
     return meetingId;
   }
 
+  // 新增：流式复制文件方法
+  Future<String> _copyFileToLocal(PlatformFile file) async {
+    final directory = await getApplicationDocumentsDirectory();
+    final directoryDir = Directory('${directory.path}/ExternalAudio');
+    if (!await directoryDir.exists()) {
+      await directoryDir.create(recursive: true);
+    }
+
+    final String targetPath = '${directory.path}/ExternalAudio/${file.name}';
+
+    if (file.path != null) {
+      // 如果有原始路径，直接复制文件
+      final sourceFile = File(file.path!);
+      await sourceFile.copy(targetPath);
+    } else {
+      // 如果没有路径，使用流式写入（分块处理）
+      final targetFile = File(targetPath);
+      final sink = targetFile.openWrite();
+
+      try {
+        // 分块写入，避免一次性加载大文件到内存
+        const chunkSize = 1024 * 1024; // 1MB chunks
+        final bytes = file.bytes!;
+
+        for (int i = 0; i < bytes.length; i += chunkSize) {
+          final end =
+              (i + chunkSize < bytes.length) ? i + chunkSize : bytes.length;
+          sink.add(bytes.sublist(i, end));
+
+          // 给UI线程一些时间处理其他任务
+          await Future.delayed(Duration(milliseconds: 1));
+        }
+      } finally {
+        await sink.close();
+      }
+    }
+
+    return targetPath;
+  }
+
+// 移除原来的_saveFile方法，替换为上面的_copyFileToLocal
+
   Future<String> _saveFile(PlatformFile file) async {
     final directory = await getApplicationDocumentsDirectory();
     final directoryDir = Directory('${directory.path}/ExternalAudio');