Fix missing audio file types in PrismMessages attachment conversion

[sulimanbenhalim]

Supersedes #223

The four audio file types (Base64Audio, LocalAudio, RemoteAudio, StoredAudio) were missing from the match statement in fromLaravelAttachments() so passing any audio attachment into a conversation would throw an UnhandledMatchError at runtime

Images and documents worked fine, audio was just never added to the match

Before

$message = new UserMessage('Analyze this audio', attachments: collect([
    new Base64Audio(base64_encode(file_get_contents('audio.mp3')), 'audio/mpeg'),
]));

// UnhandledMatchError: Unhandled match case

After it converts cleanly to PrismAudio just like images convert to PrismImage

GPT-4o and Gemini both support audio as conversation input so this is a real use case not a theoretical one

Added tests in PrismMessagesTest covering all four audio types plus the existing image and document paths