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/audit/service.py

@@ -9,6 +9,7 @@ from __future__ import annotations
 from sqlalchemy import select
 
 from steward.ansible.inventory_gen import run_title, scope_labels
+from steward.core.formatting import day_group
 from steward.models.alerts import AlertRule, MaintenanceWindow
 from steward.models.ansible import AnsibleRun
 from steward.models.ansible_inventory import AnsibleGroup, AnsibleTarget
@@ -207,3 +208,15 @@ def detail_facts(detail: dict, scopes: dict[str, str]) -> list[dict]:
             text = _plain(value)
         facts.append({"label": label, "text": text, "url": url})
     return facts
+
+
+def mark_day_groups(items: list[dict], tz, group: str = "", now=None) -> str:
+    """Give each newest-first entry its recency group (formatting.day_group,
+    in the reader's zone) and whether it opens one, so the page draws a
+    divider there. `group` is the one the previous page ended in: a group
+    split across pages is opened once. Returns the group this page ends in."""
+    for item in items:
+        item["group"] = day_group(item["event"].timestamp, tz, now)
+        item["opens_group"] = item["group"] != group
+        group = item["group"]
+    return group