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/views/dell_updates.py

@@ -166,7 +166,8 @@ def rollback_review(apply_id):
     except ValueError:
         flash("No apply with that id.", "warning")
         return redirect(url_for("updates_overview"))
-    return render_template("updates_rollback.html", rec=rec)
+    back = "dell" if request.args.get("back") == "dell" else "overview"
+    return render_template("updates_rollback.html", rec=rec, back=back)
 
 
 @bp.route("/rollback", methods=["POST"])