fix: 修复proxy_service和account_service中不当的顶层import

- proxy_service.py: 将requests和WhitelistManager改为函数内延迟import，
  避免启动时加载不需要的依赖；移除未使用的get_exit_ip_via_proxy导入
- account_service.py: 移除未使用的func、joinedload、AuditLog、
  user_has_permission顶层导入

web/backend/services/proxy_service.py

@@ -6,11 +6,9 @@ import threading
 import uuid
 from typing import Optional
 
-import requests as req_lib
 from sqlalchemy.orm import Session
 
 from core.douyu.proxy import resolve_working_proxy, verify_proxy_url, parse_proxy_response
-from core.douyu.whitelist import WhitelistManager, get_exit_ip_via_proxy
 from ..models import ProxyConfig as ProxyConfigModel, AuditLog
 
 
@@ -146,6 +144,8 @@ class ProxyService:
         loop: asyncio.AbstractEventLoop,
     ):
         """在线程中执行白名单测试。"""
+        import requests as req_lib
+        from core.douyu.whitelist import WhitelistManager
 
         def push(level, message):
             asyncio.run_coroutine_threadsafe(