feat: complete remaining jetstream parity implementation plan

src/NATS.Server/JetStream/Snapshots/StreamSnapshotService.cs

@@ -0,0 +1,10 @@
+namespace NATS.Server.JetStream.Snapshots;
+
+public sealed class StreamSnapshotService
+{
+    public ValueTask<byte[]> SnapshotAsync(StreamHandle stream, CancellationToken ct)
+        => stream.Store.CreateSnapshotAsync(ct);
+
+    public ValueTask RestoreAsync(StreamHandle stream, ReadOnlyMemory<byte> snapshot, CancellationToken ct)
+        => stream.Store.RestoreSnapshotAsync(snapshot, ct);
+}