fix(server): lower date backtrack limit from 90 to 31 days

Aneng only supports querying data up to 31 days back. The previous
90-day cap allowed dates that would silently fail at download time,
so restrict the POST /tasks `date` validation to a 31-day window.

inbound_verify/cli/server.py

@@ -216,9 +216,9 @@ def create_task(req: TaskRequest):
             raise HTTPException(
                 status_code=400, detail=f"date 不可为未来日期: {req.date}"
             )
-        if target_date < today - timedelta(days=90):
+        if target_date < today - timedelta(days=31):
             raise HTTPException(
-                status_code=400, detail=f"date 超出 90 天回溯上限: {req.date}"
+                status_code=400, detail=f"date 超出 31 天回溯上限: {req.date}"
             )
         if req.site == "百世":
             raise HTTPException(