Initial implementation: host lifecycle + PXE + admin dashboard

Go service for Proxmox homelab cluster provisioning. Handles PXE boot,
Proxmox autoinstall (answer file generation), cluster join via SSH,
and Infrastructure API registration.

- Host state machine (registered → pxe_ready → installing → ready)
- dnsmasq supervisor with MAC-based allowlist
- iPXE script and Proxmox answer file generation
- First-boot phone-home → cluster join → infra registration
- Operation locking with expiry (409 on conflict)
- SSE event hub for real-time dashboard updates
- Admin dashboard (host grid, detail, registration form)
- Config-driven server types with hot-reload
- Docker deployment (multi-stage fat image)

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

internal/orchestrator/runner.go

@@ -0,0 +1,51 @@
+package orchestrator
+
+import (
+	"context"
+	"fmt"
+	"log"
+
+	"provisioning/internal/events"
+	"provisioning/internal/model"
+	"provisioning/internal/statemachine"
+	"provisioning/internal/store"
+)
+
+type Runner struct {
+	Hosts  *store.Hosts
+	Ops    *store.Operations
+	Locks  *store.Locks
+	Hub    *events.Hub
+}
+
+func (r *Runner) Transition(ctx context.Context, hostID int64, trigger statemachine.Trigger) (model.HostState, error) {
+	host, err := r.Hosts.Get(ctx, hostID)
+	if err != nil {
+		return "", fmt.Errorf("transition: get host: %w", err)
+	}
+	next, err := statemachine.Next(host.State, trigger)
+	if err != nil {
+		return "", fmt.Errorf("transition: %w", err)
+	}
+	if err := r.Hosts.UpdateState(ctx, hostID, next); err != nil {
+		return "", fmt.Errorf("transition: update state: %w", err)
+	}
+	log.Printf("host %d (%s): %s -> %s [%s]", hostID, host.Hostname, host.State, next, trigger)
+	r.Hub.Publish(events.Event{
+		Name:    "host.state_changed",
+		Payload: fmt.Sprintf(`{"host_id":%d,"old_state":"%s","new_state":"%s"}`, hostID, host.State, next),
+	})
+	return next, nil
+}
+
+func (r *Runner) FailHost(ctx context.Context, hostID int64, reason string) {
+	if _, err := r.Transition(ctx, hostID, statemachine.TriggerFailed); err != nil {
+		log.Printf("host %d: failed to transition to failed state: %v", hostID, err)
+		return
+	}
+	op, err := r.Ops.GetActive(ctx, hostID)
+	if err == nil {
+		_ = r.Ops.Fail(ctx, op.ID, reason)
+	}
+	_ = r.Locks.Release(ctx, hostID)
+}