Requests a custom selection of the agh-backup path

### 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

Because routers have limited storage, backups reduce the amount of free space available to routers

### Proposed solution

choosing a backup path can alleviate this lack of space

### Alternatives considered and additional information

_No response_