feat(audit): every row keeps its date; dividers for Today, Yesterday, Last 7 days, Older (#5214)

The operator found "Today 08:03" in place of a date odd on the audit log,
and asked for the recency groups as dividers instead. |when now always
writes the date ("Thu 8 Oct 08:03"); mark_day_groups gives each entry its
group in the reader's zone, and a divider row opens each group. A scrolled
page carries the group the last one ended in, so it is not opened twice.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

steward/templates/audit/_rows.html

@@ -1,8 +1,10 @@
 {# audit/_rows.html — one page of the audit log's rows, then the sentinel that
-   loads the next page as the reader nears it (core.paging, pref 172). #}
+   loads the next page as the reader nears it (core.paging, pref 172). A
+   divider row opens each recency group: Today, Yesterday, Last 7 days, Older. #}
 {% from "_macros.html" import scroll_more, scroll_end %}
       {% for item in events %}
       {% set e = item.event %}
+      {% if item.opens_group %}<tr class="table-divider"><th colspan="5" scope="rowgroup">{{ item.group }}</th></tr>{% endif %}
       <tr>
         <td class="nowrap">{{ e.timestamp|when }}</td>
         <td class="nowrap">{{ e.username }}</td>
@@ -22,7 +24,8 @@
       </tr>
       {% endfor %}
 {% if after %}
-{{ scroll_more("/audit/?before=" ~ (after|urlencode) ~ (("&action=" ~ (action_filter|urlencode)) if action_filter else ""), cols=5) }}
+{{ scroll_more("/audit/?before=" ~ (after|urlencode) ~ (("&action=" ~ (action_filter|urlencode)) if action_filter else "")
+               ~ "&group=" ~ (last_group|urlencode), cols=5) }}
 {% else %}
 {{ scroll_end(cols=5) }}
 {% endif %}