feat(secrets): abstractions value types, enums, exceptions

ZB.MOM.WW.Secrets/src/ZB.MOM.WW.Secrets.Abstractions/SecretManifestEntry.cs

@@ -0,0 +1,21 @@
+namespace ZB.MOM.WW.Secrets.Abstractions;
+
+/// <summary>
+/// A compact per-secret manifest row used for cluster anti-entropy: it carries just
+/// enough state (name, revision, tombstone flag, timestamp) for two nodes to compare
+/// inventories and reconcile which secrets are newer without exchanging ciphertext.
+/// </summary>
+public record SecretManifestEntry
+{
+    /// <summary>The normalized secret name.</summary>
+    public required SecretName Name { get; init; }
+
+    /// <summary>Monotonic revision number used to determine which side is newer.</summary>
+    public required long Revision { get; init; }
+
+    /// <summary>When the secret was last updated (UTC).</summary>
+    public required DateTimeOffset UpdatedUtc { get; init; }
+
+    /// <summary>Whether the secret is soft-deleted (tombstoned).</summary>
+    public bool IsDeleted { get; init; }
+}