fix: auto-fix code issues (cron)

- 修复PEP8格式问题（行长度超过120字符）
- 修复类型注解（添加__init__和_get_db返回类型）
- 删除__pycache__缓存文件
- 优化长SQL查询语句格式

backend/main.py

@@ -4880,7 +4880,8 @@ async def get_multimodal_stats_endpoint(project_id: str, _=Depends(verify_api_ke
 
     # 统计跨模态关联
     cross_modal_count = conn.execute(
-        "SELECT COUNT(*) as count FROM multimodal_entity_links WHERE entity_id IN (SELECT id FROM entities WHERE project_id = ?)",
+        """SELECT COUNT(*) as count FROM multimodal_entity_links
+           WHERE entity_id IN (SELECT id FROM entities WHERE project_id = ?)""",
         (project_id,),
     ).fetchone()["count"]