refactor cluster network related constants

internal/machine/cluster/cluster.go

@@ -160,7 +160,7 @@ func (c *Cluster) AddMachine(ctx context.Context, req *pb.AddMachineRequest) (*p
 	if err != nil {
 		return nil, status.Errorf(codes.Internal, "create IPAM manager: %v", err)
 	}
-	subnet, err := ipam.AllocateSubnetLen(network.DefaultSubnetBits)
+	subnet, err := ipam.AllocateSubnetLen(DefaultSubnetBits)
 	if err != nil {
 		return nil, status.Errorf(codes.Internal, "allocate subnet for machine: %v", err)
 	}

internal/machine/cluster/ipam.go

@@ -7,6 +7,10 @@ import (
 	"net/netip"
 )
 
+const DefaultSubnetBits = 24
+
+var DefaultNetwork = netip.MustParsePrefix("10.210.0.0/16")
+
 // IPAM is an in-memory IP address manager for allocating and releasing subnets for machines from a cluster network.
 type IPAM struct {
 	network   netip.Prefix