feat: track designer downloads and notifications

backend/app/models/download.py

@@ -1,4 +1,4 @@
-from sqlalchemy import Column, Integer, DateTime, ForeignKey
+from sqlalchemy import Column, Integer, DateTime, ForeignKey, String, Float
 from sqlalchemy.sql import func
 from app.core.database import Base
 
@@ -9,5 +9,8 @@ class DownloadRecord(Base):
     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)
-    
+    designer_name = Column(String(100), nullable=True, index=True)
+    work_title = Column(String(255), nullable=True)
+    amount = Column(Float, default=0.0)
+
     downloaded_at = Column(DateTime(timezone=True), server_default=func.now())