Cardano Updates

cardano-crypto-wallet links against libsodium for Argon2id KDF and
XChaCha20-Poly1305 AEAD. Without this override, the Windows
cross-compiled DLL links against the default system libsodium, which
is not available in the Wine iserv environment (only libsodium-vrf is
present there, used by all other crypto packages).

This caused the iserv to crash (exit 1) at TH-module boundaries when
compiling cardano-wallet for Windows/ucrt64.

The merged cardano-base PR changed encryptedCreateDirectWithTweak,
encryptedValidatePassphrase, and encryptedKeyMaterial to return IO
instead of pure Either, since they operate on locked memory.

- Bump SRP tag to cb068e0 (merged HEAD of cardano-base master)
- mkV2Credentials: lift to IO, bind encryptedCreateDirectWithTweak
- attachPrivateKeyFromPwd: bind mkV2Credentials with <-
- withRootKey: separate STM read from IO validation so
  encryptedValidatePassphrase can run outside atomically
- migrateV1toV2: bind encryptedCreateDirectWithTweak with >>=
- decryptV2: lift to IO; use mlsbToByteString + mlsbFinalize instead
  of BA.convert (MLockedSizedBytes has no ByteArrayAccess instance)