feat(localdb): periodic oplog maintenance service (caps enforcement + tombstone pruning, both roles)

Claude-Session: https://claude.ai/code/session_01BL2Vu1ESDQ9SCN4gVKkdts

ZB.MOM.WW.LocalDb/src/ZB.MOM.WW.LocalDb.Replication/ReplicationOptions.cs

@@ -29,6 +29,9 @@ public sealed class ReplicationOptions
     /// <summary>Upper bound on the exponential reconnect backoff.</summary>
     public TimeSpan ReconnectBackoffMax { get; set; } = TimeSpan.FromSeconds(60);
 
+    /// <summary>How often the maintenance service enforces the oplog caps and prunes expired tombstones.</summary>
+    public TimeSpan MaintenanceInterval { get; set; } = TimeSpan.FromSeconds(60);
+
     /// <summary>Maximum tolerated HLC drift where a peer's clock runs ahead of ours.</summary>
     public TimeSpan MaxHlcDriftAhead { get; set; } = TimeSpan.FromMinutes(5);