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/db_manager.py

@@ -17,7 +17,6 @@ DB_PATH = os.getenv("DB_PATH", "/app/data/insightflow.db")
 # Constants
 UUID_LENGTH = 8  # UUID 截断长度
 
-
 @dataclass
 class Project:
     id: str
@@ -26,7 +25,6 @@ class Project:
     created_at: str = ""
     updated_at: str = ""
 
-
 @dataclass
 class Entity:
     id: str
@@ -47,7 +45,6 @@ class Entity:
         if self.attributes is None:
             self.attributes = {}
 
-
 @dataclass
 class AttributeTemplate:
     """属性模板定义"""
@@ -68,7 +65,6 @@ class AttributeTemplate:
         if self.options is None:
             self.options = []
 
-
 @dataclass
 class EntityAttribute:
     """实体属性值"""
@@ -89,7 +85,6 @@ class EntityAttribute:
         if self.options is None:
             self.options = []
 
-
 @dataclass
 class AttributeHistory:
     """属性变更历史"""
@@ -103,7 +98,6 @@ class AttributeHistory:
     changed_at: str = ""
     change_reason: str = ""
 
-
 @dataclass
 class EntityMention:
     id: str
@@ -114,7 +108,6 @@ class EntityMention:
     text_snippet: str
     confidence: float = 1.0
 
-
 class DatabaseManager:
     def __init__(self, db_path: str = DB_PATH):
         self.db_path = db_path
@@ -1401,11 +1394,9 @@ class DatabaseManager:
         conn.close()
         return stats
 
-
 # Singleton instance
 _db_manager = None
 
-
 def get_db_manager() -> DatabaseManager:
     global _db_manager
     if _db_manager is None: