Because:
- The v1 approve page and the v2 QR page used router state `totpComplete` as proof of a TOTP code.
- Router state does not record a verified code, so the pages must ask the gate each time.
This commit:
- Removes the `totpComplete` short-circuit from `Pair/AuthAllow` and the `ScanQR` container.
- Makes both pages always call `pairingRequiresTotp`.
- Removes the unused `useLocation` from both pages.
- Updates the comments in `Pair/Index` and `EnterTotp`.
- Adds and changes tests for the redirect and for a fresh `totpVerifiedAt`.
Closes FXA-14194