feat: improve traffic reset precision and admin features

- Increase traffic reset granularity to seconds
- Add next reset time display in admin pane

public/assets/admin/locales/en-US.js

@@ -2310,6 +2310,7 @@ window.XBOARD_TRANSLATIONS['en-US'] = {
       "commission": "Commission",
       "register_time": "Register Time",
       "actions": "Actions",
+      "next_reset_at": "Next Reset At",
       "device_limit": {
         "unlimited": "No device limit",
         "limited": "Maximum {{count}} devices allowed"

public/assets/admin/locales/zh-CN.js

@@ -2383,6 +2383,7 @@ window.XBOARD_TRANSLATIONS['zh-CN'] = {
       "commission": "佣金",
       "register_time": "注册时间",
       "actions": "操作",
+      "next_reset_at": "下次重置时间",
       "device_limit": {
         "unlimited": "无设备数限制",
         "limited": "最多可同时在线 {{count}} 台设备"