feat(ui): audit log, alert history and Ansible runs load as you scroll (#5211)

#5211 "Lists load as you scroll: audit, alert history, Ansible runs"
(milestone 477), per preference 172.

- core/paging.py: keyset paging over (time, id), newest first, with an
  opaque "<iso>|<id>" cursor; a page reads one row past itself to know
  whether another follows. No OFFSET, so rows added while someone scrolls
  never shift the pages after them.
- _macros.html scroll_more / scroll_end and static/scroll-more.js, written
  once: an IntersectionObserver with a 600px margin fetches the next page
  before the reader reaches the end; "Loading more…" while in flight,
  "End of the list." at the end, and a failed page says so with a Retry
  button instead of re-firing on every scroll.
- Audit log: no "Load more" link and no 500-row cap.
- Alert history: no 200-row stop with "pick a shorter range";
  alert_svc.history takes the cursor, so the MCP tool and the page share
  one query.
- Ansible runs: no silent cap of 50.

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

steward/templates/audit/list.html

@@ -27,40 +27,10 @@
       </tr>
     </thead>
     <tbody>
-      {% for item in events %}
-      {% set e = item.event %}
-      {% set d = item.detail %}
-      <tr>
-        <td style="white-space:nowrap;" title="{{ e.timestamp.strftime('%Y-%m-%d %H:%M:%S UTC') }}">{{ e.timestamp|ago }}</td>
-        <td style="font-size:0.85rem;">{{ e.username }}</td>
-        <td><span class="mono">{{ e.action }}</span></td>
-        <td>
-          {% if item.entity %}
-          <span class="field-hint">{{ e.entity_type|replace('_', ' ') }}</span>
-          {% if item.entity.url %}<a href="{{ item.entity.url }}">{{ item.entity.label }}</a>{% else %}{{ item.entity.label }}{% endif %}
-          {% if item.entity.gone %}<span class="field-hint">(deleted)</span>{% endif %}
-          {% elif e.entity_type %}<span class="field-hint">{{ e.entity_type|replace('_', ' ') }}</span>{% endif %}
-        </td>
-        <td style="font-size:0.8rem;color:var(--text-muted);max-width:340px;">
-          {% if d %}
-          {% for k, v in d.items() %}
-          <span style="color:var(--text-dim);">{{ k }}:</span>
-          <span class="mono">{{ v }}</span>
-          {% if not loop.last %} &nbsp;·&nbsp; {% endif %}
-          {% endfor %}
-          {% endif %}
-        </td>
-      </tr>
-      {% endfor %}
+      {% include "audit/_rows.html" %}
     </tbody>
   </table>
 </div>
-<p style="font-size:0.78rem;color:var(--text-dim);margin-top:0.75rem;">
-  Showing last {{ limit }} events.
-  {% if events | length == limit %}
-  <a href="?limit={{ limit * 2 }}{% if action_filter %}&action={{ action_filter }}{% endif %}">Load more</a>
-  {% endif %}
-</p>
 {% else %}
 <div class="card">{{ empty_state("No audit events recorded yet.") }}</div>
 {% endif %}