Minor usability and security updates

New features

• Two-factor authentication is available to user accounts (activate from My Account page).

Improvements

• Pages with tabs now remember the selected tab, so reloading the page keeps you on the same tab.
• Updates to layout and elements for accessibility, to better conform with WGAC standards (not complete yet, work continues).
• Improved login and account security. If some actions stop working, restart your browser and clear its cache. Please remember that external scripts and automation tools are not allowed.

Fixes

• The weekly financial estimate on the aircraft page now shows only that aircraft's own flights when several aircraft share a 7-day schedule.
• Route demand no longer drops sharply when a new airport replaces a closed one.
• Opening a new route from the Open Route page now works when the new route editor is set as the default.
• Airport slot handling fixes in new and old route editor's; their data matches now.