feat(api): fleet data model Phase A — License -> Host -> Instance

Migration 022 adds agent_hosts / game_instances / instance_clusters /
instance_stats (named agent_hosts to avoid the existing B2B hosts
table). HostAgentConsumerService now parses the full v2 heartbeat and
upserts an agent_hosts row (host metrics: cpu/mem/disk/agent version,
keyed by license_id+hostname until enrollment) plus one game_instances
row per heartbeat instance entry (state + uptime, the billing unit).
Legacy server_connections write retained so the current panel keeps
working — additive migration, nothing breaks. Staleness sweep + offline
beacon now flip agent_hosts too. cluster_id FK reserved for Soulmask/
Dune. Migration applied to live DB; tsc green.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

backend-nest/src/entities/agent-host.entity.ts

@@ -0,0 +1,74 @@
+import { Entity, PrimaryGeneratedColumn, Column, ManyToOne, JoinColumn, Check, Unique } from 'typeorm';
+import { License } from './license.entity';
+
+export interface AgentHostDisk {
+  mount: string;
+  total_mb: number;
+  free_mb: number;
+}
+
+/**
+ * One Corrosion host agent / one machine. Owns the machine-level facts.
+ *
+ * NOTE: distinct from the B2B `hosts` table (hosting-partner companies). This
+ * is `agent_hosts` — the physical/virtual box a customer runs the agent on.
+ */
+@Entity('agent_hosts')
+@Unique(['license_id', 'hostname'])
+@Check(`"status" IN ('connected', 'degraded', 'offline')`)
+export class AgentHost {
+  @PrimaryGeneratedColumn('uuid')
+  id: string;
+
+  @Column({ type: 'uuid' })
+  license_id: string;
+
+  @Column({ type: 'varchar', length: 255, default: '' })
+  hostname: string;
+
+  @Column({ type: 'varchar', length: 64, nullable: true })
+  agent_version: string | null;
+
+  @Column({ type: 'varchar', length: 64, nullable: true })
+  agent_commit: string | null;
+
+  @Column({ type: 'varchar', length: 32, nullable: true })
+  os: string | null;
+
+  @Column({ type: 'varchar', length: 32, nullable: true })
+  arch: string | null;
+
+  @Column({ type: 'varchar', length: 20, default: 'offline' })
+  status: string;
+
+  @Column({ type: 'timestamptz', nullable: true })
+  last_heartbeat_at: Date | null;
+
+  @Column({ type: 'double precision', nullable: true })
+  cpu_percent: number | null;
+
+  @Column({ type: 'integer', nullable: true })
+  cpu_cores: number | null;
+
+  @Column({ type: 'bigint', nullable: true })
+  mem_total_mb: number | null;
+
+  @Column({ type: 'bigint', nullable: true })
+  mem_used_mb: number | null;
+
+  @Column({ type: 'bigint', nullable: true })
+  uptime_seconds: number | null;
+
+  @Column({ type: 'jsonb', nullable: true })
+  disks: AgentHostDisk[] | null;
+
+  @Column({ type: 'timestamptz', default: () => 'NOW()' })
+  created_at: Date;
+
+  @Column({ type: 'timestamptz', default: () => 'NOW()' })
+  updated_at: Date;
+
+  @ManyToOne(() => License, { onDelete: 'CASCADE' })
+  @JoinColumn({ name: 'license_id' })
+  license: License;
+}