Fix: change filename to file in API responses for task queue display

backend/main.py

@@ -100,7 +100,7 @@ async def upload_file(file: UploadFile = File(...)):
     
     return {
         "task_id": task_id,
-        "filename": file.filename,
+        "file": file.filename,
         "status": "queued",
         "message": "Файл добавлен в очередь обработки",
     }
@@ -119,7 +119,7 @@ async def upload_batch(files: List[UploadFile] = File(...)):
         task_id = await enqueue(file_path)
         results.append({
             "task_id": task_id,
-            "filename": file.filename,
+            "file": file.filename,
             "status": "queued",
         })