enrich the invitation link and related informationev

app/models/workspace.py

@@ -19,9 +19,18 @@ class WorkspaceMember(Base, AutoID):
 
     workspace_id = Column(String(32), ForeignKey("workspaces.id", ondelete="CASCADE"), index=True)
     user_id = Column(String(32), ForeignKey("users.id", ondelete="CASCADE"), index=True)
+
+    # 允许 user_id 为空，因为被邀请的人可能还没注册系统，我们先记录他的邮箱
+    user_id = Column(String(32), ForeignKey("users.id", ondelete="CASCADE"), nullable=True, index=True)
+    invite_email = Column(String, nullable=True) # 收到邀请的邮箱
     
+    # 状态：'pending' (等待加入), 'active' (已加入), 'disabled' (已禁用)
+    status = Column(String, default="pending", nullable=False)
     # 角色权限：'owner' (所有者), 'admin' (管理员), 'user' (普通用户)
     role = Column(String, default="user", nullable=False)
+    
+    invite_token = Column(String, nullable=True, unique=True)
+    token_expires_at = Column(DateTime(timezone=True), nullable=True)
 
     created_at = Column(DateTime(timezone=True), server_default=func.now())