fix(transport): serialise the export content once and pack those bytes (review 2026-10-21 04/P8a)

src/ZB.MOM.WW.ScadaBridge.Transport/Serialization/BundleSerializer.cs

@@ -57,6 +57,28 @@ public sealed class BundleSerializer
         BundleSecretEncryptor? encryptor)
     {
         ArgumentNullException.ThrowIfNull(content);
+        return PackContentBytes(SerializeContentBytes(content), manifest, passphrase, encryptor);
+    }
+
+    /// <summary>
+    /// Packs already-serialised content (the output of <see cref="SerializeContentBytes"/>)
+    /// and the manifest into a ZIP stream, optionally encrypting the content. Lets a caller
+    /// that has already serialised the DTO — e.g. to hash it for the manifest — pack those
+    /// same bytes instead of serialising the whole graph a second time (review 2026-10-21
+    /// 04/P8a).
+    /// </summary>
+    /// <param name="contentBytes">The serialised bundle content JSON.</param>
+    /// <param name="manifest">The bundle manifest describing the content and encryption metadata.</param>
+    /// <param name="passphrase">Passphrase used for encryption; null produces a plaintext bundle.</param>
+    /// <param name="encryptor">Encryptor required when <paramref name="passphrase"/> is supplied.</param>
+    /// <returns>A seeked-to-start <see cref="MemoryStream"/> containing the bundle ZIP archive.</returns>
+    public Stream PackContentBytes(
+        byte[] contentBytes,
+        BundleManifest manifest,
+        string? passphrase,
+        BundleSecretEncryptor? encryptor)
+    {
+        ArgumentNullException.ThrowIfNull(contentBytes);
         ArgumentNullException.ThrowIfNull(manifest);
 
         if (passphrase is not null && encryptor is null)
@@ -68,7 +90,6 @@ public sealed class BundleSerializer
             throw new ArgumentException("Manifest must carry EncryptionMetadata when packing an encrypted bundle.", nameof(manifest));
         }
 
-        var contentBytes = SerializeContentBytes(content);
         byte[] payload;
         string payloadEntryName;
         BundleManifest finalManifest;