(ui) Extend page headers across utility views

Apply the shared page-header pattern to configuration, access,
operations, retention, log, and changelog pages so the control panel
uses one consistent title, context, and action structure.

Add representative view assertions for the new page context on utility
pages.

Refs #28

src/pobsync_backend/templates/pobsync_backend/ssh_credential_generate.html

@@ -3,11 +3,16 @@
 {% block title %}Generate SSH Key | pobsync{% endblock %}
 
 {% block content %}
-  <h1>Generate SSH Key</h1>
-
-  <section class="actions" aria-label="SSH key form actions">
-    <a class="button-link" href="{% url 'ssh_credentials' %}">Back to SSH keys</a>
-  </section>
+  <header class="page-header">
+    <div class="page-title">
+      <div class="page-kicker">Access</div>
+      <h1>Generate SSH Key</h1>
+      <div class="page-subtitle">Create a pobsync-managed SSH key pair for one or more backup targets.</div>
+    </div>
+    <section class="actions" aria-label="SSH key form actions">
+      <a class="button-link" href="{% url 'ssh_credentials' %}">Back to SSH keys</a>
+    </section>
+  </header>
 
   <section class="panel">
     <h2>Create Key Pair</h2>