Bundled Adminer binary for deterministic plugin installs.

- Version: 5.4.2 (pgsql-only build)
- Source repo/tag: https://github.com/vrana/adminer/tree/v5.4.2
- Build command: `php compile.php pgsql`
- Output file: `adminer-5.4.2-pgsql.php`
- SHA256: 059505abc2b56487d78bbfbeb9485ed8c6a10fe357f4ddec9fc69b1043bff4af
- Bundled extension file: `adminer-extension.php`
- Extension SHA256: 6e2f098b172838ccb3736506867396dc0954a6383fdd7b7c5e7739ab21baafeb

The installer `scripts/setup/adminer_install.sh` verifies both checksums before
copying files to:
- `/var/www/html/adminer/adminer-core.php`
- `/var/www/html/adminer/adminer-extension.php`