feat: comment spam content checks (URL-in-email, link limits)

- check_comment_content(): new method called from validate_comment()
  - Detects URL in email field (binance.info/register?ref=... pattern)
  - Blocks comments with more URLs than max_links threshold
  - Blocks any link from first-time commenters (0 approved comments)
- New options: block_url_in_email, block_links_new_commenters, max_links
- Admin: new "Comment Spam Content" card in Honeypot tab with toggles
  and max_links numeric input

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

informatiq-toolkit.php

@@ -149,6 +149,9 @@ class InformatiQ_Toolkit {
                 'min_time'             => 3,
                 'max_time'             => 7200,
                 'retain_days'          => 90,
+                'block_url_in_email'       => 1,
+                'block_links_new_commenters' => 1,
+                'max_links'            => 2,
             ]);
         }