fix(templates): icon-only buttons, selects and delete pages have accessible names

An accessibility scan (axe-core, WCAG 2 A/AA) of every page found 87
elements without a name. Icon-only buttons and links (the navbar's
administration menu on every page, the add/create buttons, the flavor
delete and back buttons) get a title, which is also their tooltip; the
labels of the language, architecture, chipset and filter selects point
at them; the memory bar is named. The shared delete confirmation page
had an empty <title> and heading, as no view passes "title": it says
"Delete <object>". The power-off form's aria-label was misspelled.

admin/templates/admin/group_list.html

@@ -6,7 +6,7 @@
 {% block content %}
 <div class="row">
     <div class="col-lg-12">
-        <a href="{% url 'admin:group_create' %}" class="btn btn-success btn-header float-end">
+        <a href="{% url 'admin:group_create' %}" class="btn btn-success btn-header float-end" title="{% trans "Create Group" %}">
             {% bs_icon 'plus-circle-fill' %}
         </a>
         {% include 'search_block.html' %}

admin/templates/admin/user_list.html

@@ -9,7 +9,7 @@
 {% block page_heading %}{{ title }}{% endblock page_heading %}
 
 {% block page_heading_extra %}
-<a href="{% url 'admin:user_create' %}" class="btn btn-success btn-header float-end">
+<a href="{% url 'admin:user_create' %}" class="btn btn-success btn-header float-end" title="{% trans "Create User" %}">
     {% bs_icon 'plus-circle-fill' %}
 </a>
 {% include 'search_block.html' %}

admin/tests/test_views.py

@@ -39,6 +39,8 @@ class AdminTestCase(TestCase):
 
         response = self.client.get(reverse("admin:group_delete", args=[group_id]))
         self.assertEqual(response.status_code, 200)
+        # the shared confirmation page names what it deletes
+        self.assertContains(response, "<title>Delete Updated Group Test</title>", html=True)
 
         response = self.client.post(reverse("admin:group_delete", args=[group_id]))
         self.assertRedirects(response, reverse("admin:group_list"))