docs: update navigation steps for the tabbed settings menu #404

Upstream: ricochet-rs/ricochet#1472, feat(ui): collect all settings and move them as a tabbed menu

Settings moved into a single tabbed menu, so navigation instructions written against the old layout are now wrong.

This is an accuracy sweep rather than new content.
Every "Open X in ricochet" step and screenshot under admin/ needs to be checked against the tabbed menu.

Pages: all of admin/