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/assets/fp/app.js

@@ -41,10 +41,6 @@ Vue.config.ignoredElements = [/^cds-/];
     },
 
     computed: {
-      initials: function () {
-        var n = (this.session && (this.session.firstName || this.session.phone)) || '?';
-        return n.slice(0, 2).toUpperCase();
-      },
       maxStage: function () { return MAX_STAGE; },
       bothCaptured: function () {
         return this.fingers['right-thumb'].status === 'done' &&
@@ -139,17 +135,27 @@ Vue.config.ignoredElements = [/^cds-/];
         });
       },
 
+      /** The agent status tag lives in the server-rendered header. */
+      renderAgentTag: function () {
+        var el = document.getElementById('agent-status');
+        if (!el) return;
+        el.textContent = this.agent.connected ? 'Agent connected' : 'Agent offline';
+        el.setAttribute('type', this.agent.connected ? 'green' : 'red');
+        el.setAttribute('title', this.agent.version ? 'fpagent ' + this.agent.version : '');
+      },
+
       connectAgent: function () {
         var self = this;
         this.socket = io(this.session.agentUrl, { reconnectionDelayMax: 5000 });
 
-        this.socket.on('connect', function () { self.agent.connected = true; });
-        this.socket.on('disconnect', function () { self.agent.connected = false; });
-        this.socket.on('connect_error', function () { self.agent.connected = false; });
+        this.socket.on('connect', function () { self.agent.connected = true; self.renderAgentTag(); });
+        this.socket.on('disconnect', function () { self.agent.connected = false; self.renderAgentTag(); });
+        this.socket.on('connect_error', function () { self.agent.connected = false; self.renderAgentTag(); });
 
         this.socket.on('agent-hello', function (data) {
           self.agent.version = (data && data.version) || '';
           self.agent.captureAgentId = (data && data.captureAgentId) || '';
+          self.renderAgentTag();
         });
 
         this.socket.on('fprint-enroll-status', function (data) {