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/export_manager.py

@@ -22,14 +22,7 @@ try:
     from reportlab.lib.pagesizes import A4
     from reportlab.lib.styles import ParagraphStyle, getSampleStyleSheet
     from reportlab.lib.units import inch
-    from reportlab.platypus import (
-        PageBreak,
-        Paragraph,
-        SimpleDocTemplate,
-        Spacer,
-        Table,
-        TableStyle,
-    )
+    from reportlab.platypus import PageBreak, Paragraph, SimpleDocTemplate, Spacer, Table, TableStyle
 
     REPORTLAB_AVAILABLE = True
 except ImportError:
@@ -194,20 +187,16 @@ class ExportManager:
             f'fill="white" stroke="#bdc3c7" rx="5"/>'
         )
         svg_parts.append(
-            f'<text x="{legend_x}" y="{legend_y}" font-size="12" font-weight="bold" '
-            f'fill="#2c3e50">实体类型</text>'
+            f'<text x="{legend_x}" y="{legend_y}" font-size="12" font-weight="bold" ' f'fill="#2c3e50">实体类型</text>'
         )
 
         for i, (etype, color) in enumerate(type_colors.items()):
             if etype != "default":
                 y_pos = legend_y + 25 + i * 20
-                svg_parts.append(
-                    f'<circle cx="{legend_x + 10}" cy="{y_pos}" r="8" fill="{color}"/>'
-                )
+                svg_parts.append(f'<circle cx="{legend_x + 10}" cy="{y_pos}" r="8" fill="{color}"/>')
                 text_y = y_pos + 4
                 svg_parts.append(
-                    f'<text x="{legend_x + 25}" y="{text_y}" font-size="10" '
-                    f'fill="#2c3e50">{etype}</text>'
+                    f'<text x="{legend_x + 25}" y="{text_y}" font-size="10" ' f'fill="#2c3e50">{etype}</text>'
                 )
 
         svg_parts.append("</svg>")
@@ -320,7 +309,6 @@ class ExportManager:
         Returns:
             CSV 字符串
         """
-        import csv
 
         output = io.StringIO()
         writer = csv.writer(output)
@@ -586,7 +574,7 @@ class ExportManager:
 _export_manager = None
 
 
-def get_export_manager(db_manager=None):
+def get_export_manager(db_manager=None) -> None:
     """获取导出管理器实例"""
     global _export_manager
     if _export_manager is None: