Webapp redesign: fixes from the functional regression test

- Unattend: a command's '...' menu stayed open after Move up/down and
  covered the next row's menu, so the next click could stage removing the
  wrong command. The menu now closes and focus returns to its button.
- '...' menus close on an outside click, on Escape and when another
  opens (static/app.js), for every page.
- Drivers: Remove asks to confirm again, as before the redesign. Long zip
  paths in a row body wrap (the page scrolled sideways at 390 px).
- Rollback review returns to the page it was opened from (Dell page or
  Updates overview), for both Cancel and the rollback itself.
- To-do: the ServiceNow period offers a year again (366 days).
- Imaging floor: a search that matches a log-only bay opens that group;
  its open state survives the live refresh. 'Clear all' states the
  number of session files it deletes, hidden finished ones included.
- Dashboard: the image key pattern is valid under the browser's v flag
  (client-side validation was silently skipped).
- Import: allowed_import_source() compares real paths, so
  '<upload dir>/../..' is refused. This path traversal predates the
  redesign; the import moves the source tree, so it mattered.

webapp/templates/updates_rollback.html

@@ -54,12 +54,12 @@
   </ul>
 
   <div style="display: flex; flex-wrap: wrap; gap: 10px; justify-content: flex-end">
-    <a class="ui-btn" href="{{ url_for('updates_overview') }}">Cancel</a>
+    <a class="ui-btn" href="{{ url_for('dell_updates.page') if back == 'dell' else url_for('updates_overview') }}">Cancel</a>
     {% if rec.unchanged and not rec.rolled_back %}
     <form method="post" action="{{ url_for('dell_updates.rollback') }}" style="margin: 0">
       <input type="hidden" name="_csrf_token" value="{{ csrf_token() }}">
       <input type="hidden" name="apply_id" value="{{ rec.id }}">
-      <input type="hidden" name="next" value="overview">
+      {% if back != 'dell' %}<input type="hidden" name="next" value="overview">{% endif %}
       <button type="submit" class="ui-btn pri">Roll back {{ rec.unchanged }} file{{ 's' if rec.unchanged != 1 }}</button>
     </form>
     {% endif %}