feat(brand): switch user-facing copy + Mercure topic prefix to wevisto.com

Mercure topic identifiers updated in lockstep across PHP publisher + TS
subscriber (and their tests). Help-page setup instructions now point to
wevisto.com. Traefik already serves both hosts; this aligns the in-app
references with the public brand.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

public/build/index.html

@@ -14,7 +14,7 @@
     <meta name="mobile-web-app-capable" content="yes" />
     <meta name="apple-mobile-web-app-status-bar-style" content="default" />
     <meta name="apple-mobile-web-app-title" content="pictureFrame" />
-    <script type="module" crossorigin src="/build/assets/index-gq5B6HCm.js"></script>
+    <script type="module" crossorigin src="/build/assets/index-ClBfMwfs.js"></script>
     <link rel="modulepreload" crossorigin href="/build/assets/_plugin-vue_export-helper-BNDVmFr7.js">
     <link rel="stylesheet" crossorigin href="/build/assets/index-BlLBHR1q.css">
   </head>