Add comment spam classification and captcha checks.

Score artwork comments with local signatures plus Together AI, and optionally require Turnstile before posting.

app/Contracts/Moderation/CommentSpamClassifier.php

@@ -0,0 +1,10 @@
+<?php
+
+namespace App\Contracts\Moderation;
+
+use App\Data\Moderation\CommentSpamClassification;
+
+interface CommentSpamClassifier
+{
+    public function classify(string $content): CommentSpamClassification;
+}