feat: track designer downloads and notifications

backend/app/api/orders.py

@@ -9,6 +9,7 @@ from app.models.work import Work
 from app.models.order import Order, OrderStatus
 from app.models.download import DownloadRecord
 from app.schemas.order import OrderCreate, OrderResponse, PaymentResponse
+from app.services.download_tracker import record_download
 
 router = APIRouter(prefix="/orders", tags=["订单"])
 
@@ -148,17 +149,9 @@ def pay_order(
         order.status = OrderStatus.PAID
         order.paid_at = datetime.now()
         
-        # 创建下载记录
-        download_record = DownloadRecord(
-            user_id=current_user.id,
-            work_id=order.work_id,
-            order_id=order.id
-        )
-        db.add(download_record)
-        
-        # 增加作品下载量
         work = db.query(Work).filter(Work.id == order.work_id).first()
-        work.downloads += 1
+        if work:
+            record_download(db, order, work, current_user)
         
         db.commit()