GLiNet username+password auth broken

### 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)

Custom (please mention in the description)

### Installation

Custom package (OpenWrt, HomeAssistant, etc; please mention in the description)

### Setup

On a router, DHCP is handled by the router

### AdGuard Home version

0.107.73

### Action

Prior to bd3774ed69622f69e5c09b35132a4d326619627a it was possible to have both GLiNet frontend integration as well as username+password basic auth to access AGH API.

Since updating to newer versions of AGH on GLiNet routers, users must choose one and break the other.

### Expected result

Expect it to work as it did before; both GLiNet and basic auth supported simultaneously.

### Actual result

`401` on basic auth API requests with `--glinet` mode. Without the `--glinet` flag the AGH frontend needs separate authentication from the GLiNet frontend.

### Additional information and/or screenshots

See forum thread: https://forum.gl-inet.com/t/adguard-home-api-access-broken-after-v4-9-0-firmware-upgrade-requires-gl-inet-admin-token