feat: track designer downloads and notifications

backend/app/api/works.py

@@ -1,4 +1,4 @@
-from fastapi import APIRouter, Depends, HTTPException, status, Query, Header
+from fastapi import APIRouter, Depends, HTTPException, status, Query, Header, BackgroundTasks
 from fastapi.responses import FileResponse
 from sqlalchemy.orm import Session
 from sqlalchemy import desc
@@ -13,6 +13,7 @@ from app.models.user import User
 from app.core.security import decode_access_token
 from app.core.config import settings
 from app.schemas.work import WorkResponse, WorkListResponse
+from app.services.download_tracker import notify_download
 
 router = APIRouter(prefix="/works", tags=["作品"])
 
@@ -126,6 +127,7 @@ def get_current_user(authorization: str = Header(None), db: Session = Depends(ge
 @router.get("/{work_id}/download", summary="下载作品原图")
 def download_work(
     work_id: int,
+    background_tasks: BackgroundTasks,
     current_user: User = Depends(get_current_user),
     db: Session = Depends(get_db)
 ):
@@ -165,6 +167,8 @@ def download_work(
             status_code=status.HTTP_404_NOT_FOUND,
             detail="文件不存在"
         )
+
+    background_tasks.add_task(notify_download, work, current_user, paid_order)
     
     # 返回文件
     filename = os.path.basename(full_path)