Dell updates: say when the results predate the last apply

After an apply the tables still showed the check from before it, so a pack
just applied looked like it still needed updating until the next check.

webapp/templates/updates_dell.html

@@ -92,6 +92,11 @@
       {% endif %}
       {% if scan %}
       <div>Last check: <strong>{{ scan.checked | local_dt }}</strong></div>
+      {% if history and history[0].at and scan.checked and history[0].at > scan.checked %}
+      <div class="alert alert-warning py-2 my-2"><i class="bi bi-info-circle"></i>
+        These results are from before the last apply ({{ history[0].at | local_dt }}), so rows it changed can still
+        show as updates. Run <strong>Check for updates</strong> again to refresh them.</div>
+      {% endif %}
       <div class="small text-muted">
         {% set cats = scan.catalogs or {} %}
         Driver pack catalog dated <span class="mono">{{ cats.drivers | local_dt }}</span>,