feat(fleet): remove host — DELETE /api/fleet/hosts/:id + Fleet card action

Self-service host removal. DELETE /api/fleet/hosts/:id (server.manage,
tenant-guarded): refuses while the host is 'connected' (409 — a live
agent re-registers on its next heartbeat, stop it first), deletes the
host's game_instances explicitly (FK is SET NULL, would otherwise
orphan them; instance_stats cascade), and clears the legacy
server_connections row if it was the license's last host. Fleet view:
offline host cards get a Remove button with inline confirm + toast.

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

frontend/src/stores/fleet.ts

@@ -77,11 +77,22 @@ export const useFleetStore = defineStore('fleet', () => {
     }
   }
 
+  /**
+   * Remove a host and its instances. Throws on failure (e.g. 409 when the host
+   * is still online) so the caller can surface the message; refetches on
+   * success.
+   */
+  async function removeHost(hostId: string): Promise<void> {
+    await api.del(`/fleet/hosts/${hostId}`)
+    await fetchFleet()
+  }
+
   return {
     hosts,
     summary,
     loading,
     error,
     fetchFleet,
+    removeHost,
   }
 })

frontend/src/views/admin/FleetView.vue

@@ -12,9 +12,10 @@
  *
  * No fabricated data. All nulls render as '—' via safeFixed/safeDate.
  */
-import { onMounted, computed } from 'vue'
+import { onMounted, computed, ref } from 'vue'
 import { useRouter } from 'vue-router'
 import { useFleetStore } from '@/stores/fleet'
+import { useToastStore } from '@/stores/toast'
 import type { FleetHost } from '@/stores/fleet'
 import { safeFixed, safeDate } from '@/utils/formatters'
 import Panel from '@/components/ds/data/Panel.vue'
@@ -30,6 +31,7 @@ import Icon from '@/components/ds/core/Icon.vue'
 // ---------------------------------------------------------------------------
 const fleet = useFleetStore()
 const router = useRouter()
+const toast = useToastStore()
 
 onMounted(() => {
   fleet.fetchFleet()
@@ -40,6 +42,25 @@ onMounted(() => {
 // ---------------------------------------------------------------------------
 const hasHosts = computed(() => fleet.hosts.length > 0)
 
+// ---------------------------------------------------------------------------
+// Remove host (offline only — a live agent re-registers)
+// ---------------------------------------------------------------------------
+const confirmHostId = ref<string | null>(null)
+const removingHostId = ref<string | null>(null)
+
+async function removeHost(host: FleetHost) {
+  removingHostId.value = host.id
+  try {
+    await fleet.removeHost(host.id)
+    toast.success(`Removed ${host.hostname}`)
+  } catch (e) {
+    toast.error(e instanceof Error ? e.message : 'Failed to remove host')
+  } finally {
+    removingHostId.value = null
+    confirmHostId.value = null
+  }
+}
+
 /** Map host status → Badge tone */
 function hostTone(status: string): 'online' | 'offline' | 'warn' {
   if (status === 'connected') return 'online'
@@ -184,6 +205,24 @@ function relativeHeartbeat(iso: string | null): string {
                 <span class="fleet-host__meta-item" v-if="host.os || host.arch">
                   <Icon name="cpu" :size="12" />{{ [host.os, host.arch].filter(Boolean).join(' / ') }}
                 </span>
+                <!-- Remove host — offline only; a live agent re-registers -->
+                <template v-if="confirmHostId === host.id">
+                  <span class="fleet-host__confirm">Remove host &amp; its instances?</span>
+                  <Button
+                    variant="danger-soft"
+                    size="sm"
+                    :loading="removingHostId === host.id"
+                    @click="removeHost(host)"
+                  >Remove</Button>
+                  <Button variant="ghost" size="sm" :disabled="removingHostId === host.id" @click="confirmHostId = null">Cancel</Button>
+                </template>
+                <Button
+                  v-else-if="host.status !== 'connected'"
+                  variant="ghost"
+                  size="sm"
+                  icon="trash-2"
+                  @click="confirmHostId = host.id"
+                >Remove</Button>
               </div>
             </div>