feat: show Ubuntu phased updates apart and leave them out of pending counts

apt lists phased updates as upgradable while an upgrade defers them until
Ubuntu selects the host, so a freshly patched server kept reporting pending
updates. The agent now flags them; the server stores the flag and leaves them
out of patch run counts, and the server page shows them in their own section.

server/internal/grpc/server.go

@@ -103,6 +103,7 @@ func (s *vantageServer) ReportUpdates(ctx context.Context, req *pb.ReportUpdates
 			Name:           u.Name,
 			CurrentVersion: u.CurrentVersion,
 			NewVersion:     u.NewVersion,
+			Phased:         u.Phased,
 		}
 	}
 	if err := services.StoreAvailableUpdates(srv.ServerID, pkgs); err != nil {