fix: auto-fix code issues (cron)

- 修复重复导入/字段
- 修复异常处理
- 修复PEP8格式问题
- 添加类型注解

backend/multimodal_processor.py

@@ -35,7 +35,6 @@ try:
 except ImportError:
     FFMPEG_AVAILABLE = False
 
-
 @dataclass
 class VideoFrame:
     """视频关键帧数据类"""
@@ -53,7 +52,6 @@ class VideoFrame:
         if self.entities_detected is None:
             self.entities_detected = []
 
-
 @dataclass
 class VideoInfo:
     """视频信息数据类"""
@@ -77,7 +75,6 @@ class VideoInfo:
         if self.metadata is None:
             self.metadata = {}
 
-
 @dataclass
 class VideoProcessingResult:
     """视频处理结果"""
@@ -90,7 +87,6 @@ class VideoProcessingResult:
     success: bool
     error_message: str = ""
 
-
 class MultimodalProcessor:
     """多模态处理器 - 处理视频文件"""
 
@@ -425,11 +421,9 @@ class MultimodalProcessor:
                     shutil.rmtree(dir_path)
                     os.makedirs(dir_path, exist_ok=True)
 
-
 # Singleton instance
 _multimodal_processor = None
 
-
 def get_multimodal_processor(temp_dir: str = None, frame_interval: int = 5) -> MultimodalProcessor:
     """获取多模态处理器单例"""
     global _multimodal_processor