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/metadata.go

@@ -6,11 +6,13 @@ import (
 
 // VaultMetadata contains information about a vault
 type VaultMetadata struct {
-	CreatedAt          time.Time `json:"createdAt"`
-	Description        string    `json:"description,omitempty"`
-	DerivationIndex    uint32    `json:"derivation_index"`
-	PublicKeyHash      string    `json:"public_key_hash,omitempty"`      // Double SHA256 hash of the actual long-term public key
-	MnemonicFamilyHash string    `json:"mnemonic_family_hash,omitempty"` // Double SHA256 hash of index-0 key (for grouping vaults from same mnemonic)
+	CreatedAt       time.Time `json:"createdAt"`
+	Description     string    `json:"description,omitempty"`
+	DerivationIndex uint32    `json:"derivation_index"`
+	// Double SHA256 hash of the actual long-term public key
+	PublicKeyHash string `json:"public_key_hash,omitempty"`
+	// Double SHA256 hash of index-0 key (for grouping vaults from same mnemonic)
+	MnemonicFamilyHash string `json:"mnemonic_family_hash,omitempty"`
 }
 
 // UnlockerMetadata contains information about an unlocker