- Record device online/offline, remote SSH, Web and Control sessions
- Add device_event_logs table with MAC, event type and time range indexes
- Distinguish remote_control vs remote_web by device client type
- Admin-only log page with device/access tabs, duration column and filters
- Permission-gated sidebar entry (device_log.read)
Signed-off-by: GL.iNet-Yongping.Xie <yongping.xie@gl-inet.com>