add:解决select可跳过次数限制，新增sha256加密token，限制取件码+ip+时间999s内取件

Author: vastsa

main.py

@@ -1,6 +1,5 @@
 import asyncio
 import datetime
-import time
 import uuid
 from pathlib import Path
 from sqlalchemy import select, func, update
@@ -13,7 +12,6 @@
 from fastapi import FastAPI, Depends, UploadFile, Form, File, HTTPException, BackgroundTasks
 from core.database import init_models, Options, Codes, get_session
 from settings import settings
-import hashlib
 
 # 实例化FastAPI
 app = FastAPI(debug=settings.DEBUG, redoc_url=None, docs_url=None, openapi_url=None)