docs: port still-relevant WHMCS KB articles to the dedicated KB

First step of retiring the WHMCS knowledgebase in favour of
kb.anhonesthost.com. Ports the four articles that are still accurate and
product-agnostic, into three new top-level sections:

- domains/  — transferring a domain, flushing a local DNS cache
- email/    — why we filter outbound mail
- support/  — remote support via RustDesk

Content was refreshed rather than copied verbatim:
- RustDesk download links were pinned to 1.3.8; now point at /releases/latest
  (current is 1.4.9). API server switched to https, which the relay serves.
- macOS DNS flush gained the killall mDNSResponder step, without which the
  documented command usually appears to do nothing.
- The nameserver list was deliberately not ported — this KB points customers
  at Dashboard → Server Information instead of hardcoding per-server values.
- Added an anti-social-engineering warning to the remote-support page.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

src/pages/index.astro

@@ -28,6 +28,21 @@ const PRODUCT_META: Record<string, { title: string; blurb: string; firstSection:
     blurb: 'Configure Outlook, Apple Mail, Thunderbird, and mobile clients.',
     firstSection: 'index',
   },
+  domains: {
+    title: 'Domains',
+    blurb: 'Transfer a domain to us, point it at your hosting, and sort out DNS problems.',
+    firstSection: 'transferring-a-domain-to-us',
+  },
+  email: {
+    title: 'Email',
+    blurb: 'How our mail filtering works and what to do when a message does not arrive.',
+    firstSection: 'outbound-spam-filtering',
+  },
+  support: {
+    title: 'Support',
+    blurb: 'Working with our support team, including remote-assistance sessions.',
+    firstSection: 'remote-support',
+  },
 };
 
 const docs = await getCollection('docs');