Add comment spam classification and captcha checks.

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

app/Data/Moderation/CommentSpamClassification.php

@@ -0,0 +1,15 @@
+<?php
+
+namespace App\Data\Moderation;
+
+final class CommentSpamClassification
+{
+    public function __construct(
+        public readonly bool $spam,
+        public readonly float $confidence,
+        public readonly string $reason,
+        public readonly string $provider,
+        public readonly string $model,
+        public readonly int $latencyMs,
+    ) {}
+}