The setup guides walked the retired broadcast-list approve ("your device
appears under Pending Device Registrations — click Approve"), which no
longer exists. Both now describe the pairing-code flow: the e-reader
displays a 6-digit code, you type it into Pair a Device on your own
account, and only whoever holds the device can read the code — the
family-server gap that motivated the change. Adds a Pairing Code Not
Accepted troubleshooting case, refreshes the security practices
(claim only codes you can see on a device you are holding), and aligns
the remaining approval/pending wording throughout.