chore: initialize tuhui repository

backend/app/models/download.py

@@ -0,0 +1,13 @@
+from sqlalchemy import Column, Integer, DateTime, ForeignKey
+from sqlalchemy.sql import func
+from app.core.database import Base
+
+class DownloadRecord(Base):
+    __tablename__ = "download_records"
+    
+    id = Column(Integer, primary_key=True, index=True)
+    user_id = Column(Integer, ForeignKey("users.id"), nullable=False, index=True)
+    work_id = Column(Integer, ForeignKey("works.id"), nullable=False, index=True)
+    order_id = Column(Integer, ForeignKey("orders.id"), nullable=False, index=True)
+    
+    downloaded_at = Column(DateTime(timezone=True), server_default=func.now())