chore: extract account constant

Co-authored-by: Steven Johnson <[email protected]>

catalyst_voices/packages/internal/catalyst_voices_services/lib/src/crypto/key_derivation.dart

@@ -6,7 +6,7 @@ final class KeyDerivation {
   /// See: https://github.com/input-output-hk/catalyst-voices/pull/1300
   static const int _purpose = 508;
   static const int _type = 139;
-
+static const int _account = 0; // Future Use
   final CatalystKeyDerivation _keyDerivation;
 
   const KeyDerivation(this._keyDerivation);
@@ -49,6 +49,6 @@ final class KeyDerivation {
   /// The path feed into key derivation algorithm
   /// to generate a key pair from a seed phrase.
   String _roleKeyDerivationPath(AccountRole role) {
-    return "m/$_purpose'/$_type'/0'/${role.number}/0";
+    return "m/$_purpose'/$_type'/$_account'/${role.number}/0";
   }
 }