Migrate instances when draining and verify hosts before enabling

src/lib/hosts.ts

@@ -94,6 +94,7 @@ export interface Host {
     enrolled: boolean; credentialActive: boolean;
     decommission: HostDecommission | null;
     preparation?: HostPreparation;
+    enablingSince?: string | null;
 }
 export interface HostOperation {
     id: string; hostId: string; kind: string; instanceId: string | null; generation: number | null;