feat: add durable security activity center (Closes #493)

frontend/index.html

@@ -38,6 +38,15 @@
     <div id="active-devices-status" class="small" role="status" aria-live="polite"></div>
     <button id="enroll-passkey" type="button">Add a passkey for this device</button>
     <div id="active-devices-list" class="active-devices-list"></div>
+    <section class="security-activity" aria-labelledby="security-activity-title">
+      <div class="security-activity-header">
+        <h3 id="security-activity-title">Security activity</h3>
+        <p class="small muted">Recent sign-ins, device changes, and protected actions.</p>
+      </div>
+      <div id="security-activity-status" class="small" role="status" aria-live="polite"></div>
+      <div id="security-activity-list" class="security-activity-list"></div>
+      <button id="load-more-security-activity" type="button" hidden>Load older activity</button>
+    </section>
   </section>
 </div>