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/pgpunlocker.go

@@ -129,6 +129,7 @@ func (p *PGPUnlocker) GetID() string {
 		// We cannot continue with a fallback ID as that would mask data corruption
 		panic(fmt.Sprintf("PGP unlocker metadata is corrupt or missing GPG key ID: %v", err))
 	}
+
 	return fmt.Sprintf("%s-pgp", gpgKeyID)
 }
 
@@ -139,6 +140,7 @@ func (p *PGPUnlocker) Remove() error {
 	if err := p.fs.RemoveAll(p.Directory); err != nil {
 		return fmt.Errorf("failed to remove PGP unlocker directory: %w", err)
 	}
+
 	return nil
 }
 
@@ -177,6 +179,7 @@ func generatePGPUnlockerName() (string, error) {
 
 	// Format: hostname-pgp-YYYY-MM-DD
 	enrollmentDate := time.Now().Format("2006-01-02")
+
 	return fmt.Sprintf("%s-pgp-%s", hostname, enrollmentDate), nil
 }
 
@@ -320,7 +323,9 @@ func CreatePGPUnlocker(fs afero.Fs, stateDir string, gpgKeyID string) (*PGPUnloc
 		return nil, fmt.Errorf("failed to marshal unlocker metadata: %w", err)
 	}
 
-	if err := afero.WriteFile(fs, filepath.Join(unlockerDir, "unlocker-metadata.json"), metadataBytes, FilePerms); err != nil {
+	if err := afero.WriteFile(fs,
+		filepath.Join(unlockerDir, "unlocker-metadata.json"),
+		metadataBytes, FilePerms); err != nil {
 		return nil, fmt.Errorf("failed to write unlocker metadata: %w", err)
 	}
 
@@ -377,6 +382,7 @@ func checkGPGAvailable() error {
 	if err := cmd.Run(); err != nil {
 		return fmt.Errorf("GPG not available: %w (make sure 'gpg' command is installed and in PATH)", err)
 	}
+
 	return nil
 }