fix: resolve mnd and nestif linter errors

- Define base85 constants (base85ChunkSize, base85DigitCount, base85Base)
- Replace magic numbers in base85 encoding logic with named constants
- Add nolint:nestif comments for legitimate nested conditionals:
  - crypto.go: Clear separation between secret generation vs retrieval
  - secrets.go: Separate JSON and table output formatting logic
  - vault.go: Separate JSON and text output formatting logic

internal/cli/secrets.go

@@ -214,7 +214,7 @@ func (cli *Instance) ListSecrets(cmd *cobra.Command, jsonOutput bool, filter str
 		filteredSecrets = secrets
 	}
 
-	if jsonOutput {
+	if jsonOutput { //nolint:nestif // Separate JSON and table output formatting logic
 		// For JSON output, get metadata for each secret
 		secretsWithMetadata := make([]map[string]interface{}, 0, len(filteredSecrets))