create workspace table & workspace-user membership

app/models/workspace.py

@@ -0,0 +1,31 @@
+from sqlalchemy import Column, DateTime, String, ForeignKey, BigInteger, UniqueConstraint
+from sqlalchemy.sql import func
+from .base import AutoID, Base
+
+class Workspace(Base, AutoID):
+    """工作区表"""
+    __tablename__ = "workspaces"
+
+    name = Column(String, nullable=False)
+    # 存储容量上限（单位：字节 Bytes），默认 5GB
+    storage_limit = Column(BigInteger, default=5 * 1024 * 1024 * 1024) 
+
+    created_at = Column(DateTime(timezone=True), server_default=func.now())
+
+
+class WorkspaceMember(Base, AutoID):
+    """工作区成员及权限表"""
+    __tablename__ = "workspace_members"
+
+    workspace_id = Column(String(32), ForeignKey("workspaces.id", ondelete="CASCADE"), index=True)
+    user_id = Column(String(32), ForeignKey("users.id", ondelete="CASCADE"), index=True)
+    
+    # 角色权限：'owner' (所有者), 'admin' (管理员), 'user' (普通用户)
+    role = Column(String, default="user", nullable=False)
+
+    created_at = Column(DateTime(timezone=True), server_default=func.now())
+
+    # 一个用户在一个工作区只能有一条记录
+    __table_args__ = (
+        UniqueConstraint("workspace_id", "user_id", name="uq_workspace_user"),
+    )