Summary

This PR improves Debian 13 compatibility in the additional-server validation + Docker installation path.

Root cause

In some Debian 13 environments, OS detection can rely on ID_LIKE rather than only ID, and Docker repository setup may fail when VERSION_CODENAME is numeric (13) instead of trixie.

What changed

• app/Models/Server.php

  • Refactored /etc/os-release parsing into testable helpers.
  • OS family resolution now checks ID first, then falls back to ID_LIKE.
  • Unsupported distributions are still rejected explicitly (no silent fallback).

• app/Actions/Server/InstallDocker.php

  • Debian APT fallback now normalizes codename:
    • DOCKER_VERSION_CODENAME=${VERSION_CODENAME:-${VERSION_ID}}
    • if codename is 13, map to trixie
  • Docker apt source uses normalized codename.

• Tests

  • tests/Unit/ServerOsDetectionTest.php
  • tests/Unit/Actions/Server/InstallDockerCommandTest.php

Repro / verification steps

Unit tests

php artisan test --compact tests/Unit/ServerOsDetectionTest.php
php artisan test --compact tests/Unit/Actions/Server/InstallDockerCommandTest.php

Expected:

• Debian 13 (ID=debian, VERSION_CODENAME=trixie) resolves to Debian family.
• Debian-like distro (ID_LIKE=debian) resolves to Debian family.
• Numeric codename path (VERSION_CODENAME=13) is accepted and covered.
• Unsupported distro still returns false.
• Debian Docker command contains 13 -> trixie normalization.

Manual flow (UI)

1. Add an additional server running Debian 13.
2. Run server validation + prerequisites + Docker installation.

Expected:

• Validation no longer fails due to Debian-family detection edge cases.
• Docker APT fallback uses normalized codename (trixie) when codename is numeric.

Demo checklist

• Attach short demo video (Debian 13 server validation + install flow)

/claim #8154