discard adjustable models' id prefix & payload length

app/models/project.py

@@ -1,17 +1,13 @@
-from typing import TYPE_CHECKING
 from sqlalchemy import Column, DateTime, String, ForeignKey, Integer
 from sqlalchemy.sql import func
 from .base import AutoID, Base
 
-if TYPE_CHECKING:
-    from .workspace import Workspace
-
 class ProjectItem(Base, AutoID):
     """项目与文件夹的树状虚拟文件系统"""
     __tablename__ = "project_items"
 
     workspace_id = Column(
-        String(Workspace.id_length()),
+        String(AutoID.id_length()),
         ForeignKey("workspaces.id", ondelete="CASCADE"),
         index=True,
     )