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_dell.html

@@ -490,7 +490,7 @@
         <div class="sub">Apply <span class="mono">{{ h.id }}</span>.</div>
       </div>
     </details>
-    {% if can %}<div class="act"><a class="ui-btn" href="{{ url_for('dell_updates.rollback_review', apply_id=h.id) }}">Review rollback</a></div>{% endif %}
+    {% if can %}<div class="act"><a class="ui-btn" href="{{ url_for('dell_updates.rollback_review', apply_id=h.id, back='dell') }}">Review rollback</a></div>{% endif %}
   </div>
   {% endfor %}
 </section>