discard adjustable models' id prefix & payload length

app/models/follow.py

@@ -1,25 +1,18 @@
-from typing import TYPE_CHECKING
 from sqlalchemy import Column, DateTime, String, ForeignKey, UniqueConstraint
 from sqlalchemy.sql import func
 from .base import AutoID, Base
 
-# 只有在静态检查时才导入
-# 运行阶段这段代码会被跳过，彻底避免循环导入
-# 不确定是否用得上，但感觉这是个好习惯，尤其在模型之间有外键关系时
-if TYPE_CHECKING:
-    from .user import User
-
 class Follow(Base, AutoID):
     """用户关注关系表"""
     __tablename__ = "follows"
 
     follower_id = Column(
-        String(User.id_length()), 
+        String(AutoID.id_length()), 
         ForeignKey("users.id", ondelete="CASCADE"), 
         index=True
     )
     followee_id = Column(
-        String(User.id_length()), 
+        String(AutoID.id_length()), 
         ForeignKey("users.id", ondelete="CASCADE"), 
         index=True
     )