feat(website): add the Stalker portal setup guide with mock-backed screenshots

Publish "How to Connect a Stalker or Ministra Portal to IPTVnator": the
portal URL shapes discovery accepts, MAC normalization, the optional
serial/device-ID/signature fields and the pinning rules behind the
"generate device IDs" toggle, what endpoint discovery does on Add, the
sections a portal source gets, Account info, and a troubleshooting list
built from the app's own refusal messages, plus a seven-question FAQ.
The guide is cross-linked from the download pages and llms.txt.

Guide screenshots come from the capture script. Shots that walk into a
Stalker portal start the stalker-mock-server and seed its marketing-demo
portal for that run only, so release shots never gain a third source
card. The frame guard allowlists exactly that scenario's MAC and keeps
rejecting every other MAC-shaped string.

To keep the live-TV frame free of third-party images, the fictional live
channel list and the channel-logo SVG renderer move into
@iptvnator/shared/marketing-fixtures; both mocks now serve
/assets/marketing/logo/<slug>.svg, the Stalker marketing-demo scenario
builds its ITV categories, channels and schedule from those fixtures
instead of faker names with picsum logos, and the mock resolves asset
URLs on get_all_channels too, which is the response the app renders
the channel list from.

Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>

tools/testing/website-guides.test.mjs

@@ -20,6 +20,13 @@ const GUIDES = [
       'blog/guides/screenshots/guide-xtream-live-dark.png',
     ],
   },
+  {
+    slug: 'stalker-portal-setup-guide',
+    screenshots: [
+      'blog/guides/screenshots/guide-stalker-add-playlist-dark.png',
+      'blog/guides/screenshots/guide-stalker-live-dark.png',
+    ],
+  },
 ];
 
 const readDist = (relativePath) => readFile(new URL(relativePath, distRoot), 'utf8');