loadSeed
Decrypts and returns the wallet seed material.
Shows a biometric prompt to unlock the Keystore master key, reads the encrypted seed from storage, and decrypts it. The caller MUST call PlaintextSeed.wipe as soon as signing is complete.
Parameters
activity
The FragmentActivity hosting the biometric prompt
Throws
if no seed exists
if the stored file is malformed
if the user cancelled
if biometric authentication failed