Fix EncryptWithPassphrase to accept LockedBuffer for data parameter

- Changed EncryptWithPassphrase to accept *memguard.LockedBuffer instead of []byte
- Updated all callers to pass LockedBuffer:
  - CreatePassphraseUnlocker in vault/unlockers.go
  - Keychain unlocker in keychainunlocker.go
  - Tests in passphrase_test.go
- Removed intermediate dataBuffer creation since data is now already protected
- This ensures sensitive data is protected in memory throughout encryption

internal/secret/secret.go

@@ -62,7 +62,6 @@ func NewSecret(vault VaultInterface, name string) *Secret {
 	}
 }
 
-
 // GetValue retrieves and decrypts the current version's value using the provided unlocker
 func (s *Secret) GetValue(unlocker Unlocker) ([]byte, error) {
 	DebugWith("Getting secret value",