feat(ui): ui-shell header with tool links, mobile side nav, Youreka logo

- header: Carbon ui-shell (cds-header) with the Youreka logo (from
  idid-enterprise-portal), Image Cropper / Fingerprint Agent nav items
  (aria-current on the active tool), the agent status tag on the wizard,
  and the operator chip + Sign out on desktop
- mobile: cds-side-nav (logo above the items, both tools, a divider, then
  Sign out) toggled by the ui-shell menu button; account actions move out
  of the header below 1056px, the nav is hidden at desktop widths
- the header is built once in server.js (appHeader) and injected into the
  landing, both tools and error pages — no per-page duplication
- removed my duplicate menu-button toggle: ui-shell coordinates the menu
  button and side nav itself (the duplicate cancelled it out)
- fixes: 'cds-header' was hidden by a selector-list typo
  (cds-header, cds-side-nav:not(:defined)); the collapsed side nav no
  longer captures taps

Tools banner logo asset added (public/assets/youreka-logo.png).

tools/public/index.html

@@ -8,23 +8,15 @@
   <link rel="stylesheet" href="https://cdn.jsdelivr.net/npm/@carbon/styles@1.69.0/css/styles.min.css">
   <link rel="stylesheet" href="/assets/style.css">
   <link rel="icon" href="data:image/svg+xml,<svg xmlns='http://www.w3.org/2000/svg' viewBox='0 0 24 24'><rect width='24' height='24' rx='4' fill='%230f62fe'/><path d='M12 5a6 6 0 0 0-6 6c0 2.6.8 4.1 1.5 5.2' fill='none' stroke='white' stroke-width='1.6' stroke-linecap='round'/><path d='M15.5 19a7.5 7.5 0 0 0 3-9.7A6 6 0 0 0 7.1 7.9' fill='none' stroke='white' stroke-width='1.6' stroke-linecap='round'/><path d='M9.5 18.5a5.5 5.5 0 0 1-.8-7.6 3.8 3.8 0 0 1 7.2 1.5 4.3 4.3 0 0 1-3.4 4.6' fill='none' stroke='white' stroke-width='1.6' stroke-linecap='round'/></svg>">
+  <script type="module" src="https://1.www.s81c.com/common/carbon/web-components/version/v2.50.0/ui-shell.min.js"></script>
   <script type="module" src="https://1.www.s81c.com/common/carbon/web-components/version/v2.50.0/tile.min.js"></script>
+  <script type="module" src="https://1.www.s81c.com/common/carbon/web-components/version/v2.50.0/tag.min.js"></script>
   <style>
     cds-tile:not(:defined), cds-clickable-tile:not(:defined) { visibility: hidden; }
   </style>
 </head>
 <body class="app">
-  <nav class="nav">
-    <div class="container">
-      <a class="brand" href="/">
-        <span class="brand-mark">
-          <svg viewBox="0 0 24 24" fill="none" stroke="currentColor" stroke-width="2" stroke-linecap="round" stroke-linejoin="round" aria-hidden="true"><path d="M12 2a8 8 0 0 0-8 8c0 3.5 1 5.5 2 7"/><path d="M16 21a10 10 0 0 0 4-13 8 8 0 0 0-15.7-1"/><path d="M8 21a8 8 0 0 1-1-11 5 5 0 0 1 9.7 1.4A6 6 0 0 1 12 17"/><path d="M12 21a4 4 0 0 0 4-4 4 4 0 0 0-1.2-2.9"/></svg>
-        </span>
-        YOUreka <small>Tools</small>
-      </a>
-      <div class="nav-right"><!--session-nav--></div>
-    </div>
-  </nav>
+  <!--app-header-->
 
   <main class="container">
     <div class="hero">