解决录制结束后，无法重新预览相机问题

lib/features/recording/view-model/view_model_recording.dart

@@ -196,6 +196,32 @@ class RecordingViewModel extends Notifier<RecordingModel> {
     throw StateError('initializePreview retry exhausted');
   }
 
+  /// 停止录制后重新绑定相机预览（重置 isPreviewReady 以显示加载遮罩）。
+  Future<void> restorePreview() async {
+    if (!RecordingPlatform.isSupported) return;
+
+    _updateSession((s) => s.copyWith(isPreviewReady: false, errorMessage: null));
+    try {
+      final status = await _initializePreviewWithRetry();
+      _updateSession(
+        (s) => s.copyWith(
+          status: status,
+          isPreviewReady: status.state == RecordingState.previewing,
+          errorMessage: status.state == RecordingState.previewing
+              ? null
+              : (status.message ?? '相机预览初始化失败'),
+        ),
+      );
+    } on PlatformException catch (error) {
+      _updateSession(
+        (s) => s.copyWith(
+          isPreviewReady: false,
+          errorMessage: error.message ?? '相机预览初始化失败',
+        ),
+      );
+    }
+  }
+
   List<Permission> _galleryPermissions() {
     if (Platform.isIOS) {
       return [Permission.photosAddOnly, Permission.photos];
@@ -280,6 +306,8 @@ class RecordingViewModel extends Notifier<RecordingModel> {
       _updateSession(
         (s) => s.copyWith(errorMessage: error.message ?? '停止录制失败'),
       );
+    } finally {
+      await restorePreview();
     }
   }