DHCP built in Adguard Home ignores hostname cases

### Prerequisites

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

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

- [X] I want to report a bug and not [ask a question or ask for help](https://github.com/AdguardTeam/AdGuardHome/discussions/categories/q-a)

- [X] I have set up AdGuard Home correctly and [configured clients to use it](https://github.com/AdguardTeam/AdGuardHome/wiki/Clients). (Use the [Discussions](https://github.com/AdguardTeam/AdGuardHome/discussions/categories/q-a) for help with installing and configuring clients.)

### Platform (OS and CPU architecture)

Linux, ARMv7

### Installation

GitHub releases or script from README

### Setup

On a router, DHCP is handled by AdGuard Home

### AdGuard Home version

v107.48

### Action

Using the built-in DHCP server of Adguard Home, all DHCP clients' hostnames are in lowercase. Adguard Home DHCP displays / shows all their DHCP lease hostnames in lowercase - ignoring any uppercase letters.


### Expected result

Hostnames as implemented by their devices - including uppercase and lowercase letters.

### Actual result

Using the built-in DHCP server of Adguard Home, all DHCP clients' hostnames are in lowercase. Adguard Home DHCP displays / shows all their DHCP lease hostnames in lowercase - ignoring any uppercase letters.

### Additional information and/or screenshots