Add logo click to return to customers view

Clicking the CuituNet Intra brand/logo in the header
navigates back to the Asiakkaat (customers) tab.

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

index.html

@@ -54,7 +54,7 @@
     <div id="dashboard" style="display:none">
         <header>
             <div class="header-left">
-                <div class="header-brand">
+                <div class="header-brand" id="brand-home" style="cursor:pointer;">
                     <span class="brand-icon">&#9889;</span>
                     <div>
                         <h1>CuituNet Intra</h1>