Extract hardcoded AD ports to constant for maintainability

[Copilot]

Addresses review feedback to extract hardcoded Active Directory port list to a named constant.

Changes

• Added $AD_WELL_KNOWN_PORTS constant at function scope containing AD well-known ports
• Updated Test-IsAdWellKnownPort to reference the constant instead of inline array

Before:

function Test-IsAdWellKnownPort {
    param([string]$Port)
    $valid = @('53','88','135','389','445','464','636','3268','3269')
    return ($valid -contains $Port)
}

After:

$AD_WELL_KNOWN_PORTS = @('53','88','135','389','445','464','636','3268','3269')

function Test-IsAdWellKnownPort {
    param([string]$Port)
    return ($AD_WELL_KNOWN_PORTS -contains $Port)
}

Makes future updates to the AD port list more maintainable.

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