Package request: brscan4 (Brother scanner driver)

### Problem / Motivation

Currently only available via AUR (https://aur.archlinux.org/packages/brscan4).

### Proposed Solution

Requesting inclusion in the CachyOS repo for the same reason as brlaser — trusted build/signing instead of relying on AUR PKGBUILDs pulling vendor binaries.

### Alternatives Considered

_No response_

### Additional Context
I have tried sane-airscan and it did not pick up up the scanner.

_No response_

Start by reviewing the linked AUR brscan4 package and the existing brlaser packaging referenced in the issue. Then check the CachyOS distribution's process for adding packages and verify how the vendor binaries are built and signed. Done means brscan4 is accepted into the CachyOS repository with trusted packaging.

Written by the indexing model from the issue text.