Return different DNS records based on subnet.

### 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

### The problem

A DNS server must provide different IP addresses for the same domain based on whether the request originates from a LAN or a VPN.

### Proposed solution

Implement split-horizon DNS or configure conditional DNS rules that detect the request source and respond with the appropriate IP address for LAN and VPN clients.

https://en.wikipedia.org/wiki/Split-horizon_DNS

### Alternatives considered and additional information

_No response_