fix: resolve exported type stuttering issues (revive)

- Rename VaultMetadata to Metadata in internal/vault package to avoid stuttering
- Rename BIP85DRNG to DRNG in pkg/bip85 package to avoid stuttering
- Update all references in code and tests

internal/secret/passphraseunlocker.go

@@ -121,6 +121,7 @@ func (p *PassphraseUnlocker) Remove() error {
 	if err := p.fs.RemoveAll(p.Directory); err != nil {
 		return fmt.Errorf("failed to remove passphrase unlocker directory: %w", err)
 	}
+
 	return nil
 }