add limit cap and remove unused import

encar_scraper/api/routes/tasks.py

@@ -1,7 +1,7 @@
 # Роуты запуска задач синхронизации Encar и просмотра истории sync-runs.
 
 from fastapi import APIRouter, Depends, Query
-from pydantic import BaseModel
+from pydantic import BaseModel, Field
 from sqlalchemy import select, func
 
 from ..deps import get_persistence
@@ -25,7 +25,7 @@ class SyncListingRequest(BaseModel):
     year_to: int | None = None
     price_max: int | None = None
     lane: str = "encar"
-    limit: int | None = None
+    limit: int | None = Field(default=None, le=500_000)
 
 
 @router.post("/tasks/sync-vehicle")