* feat: show Bitcoin master fingerprint in wallet keys
Add the BIP-32 master fingerprint (XFP) to the Bitcoin wallet keys shown
under Settings > Seed & Keys > Keys, labeled "Master fingerprint".
* fix: keep xPub in Keys tab by splitting silent payment keys into a dedicated list
The Keys tab / Silent Payments tab split relied on a hardcoded item index
(`items.sublist(0, 4)` / `sublist(4)`) that assumed the first four items
were always WIF/private key/public key/xPub. Adding the master fingerprint
as the first item pushed xPub into the Silent Payments tab.
Route Bitcoin silent payment keys into their own `silentPaymentItems` list
instead, and render each tab from its list.
