chore: add rInbox to r* Ecosystem footer

Add rinbox.online link to the ecosystem footer navigation.

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

portal/templates/portal/landing.html

@@ -595,6 +595,7 @@
         <a href="https://rcart.online">🛒 rCart</a>
         <a href="https://rwallet.online">💼 rWallet</a>
         <a href="https://rfiles.online" class="current">📁 rFiles</a>
+        <a href="https://rinbox.online">✉️ rInbox</a>
         <a href="https://rnetwork.online">🌐 rNetwork</a>
     </div>
     <p class="ecosystem-tagline">Part of the r* ecosystem &mdash; collaborative tools for communities.</p>