In-use indicator on static lease entries

### Prerequisites

- [X] I have checked the [Wiki](https://github.com/AdguardTeam/AdGuardHome/wiki) and [Discussions](https://github.com/AdguardTeam/AdGuardHome/discussions) and found no answer

- [X] I have searched other issues and found no duplicates

- [X] I want to request a feature or enhancement and not ask a question

### Description

I would like to see an indicator in each static lease items to see which ones are currently in-use by devices and which ones has not been requested.
In DHCP leases I see which ones have been served but not in static lease.