Реализация device-control-service: gRPC + MQTT + Device Shadow в Redis

Добавлен gRPC-контракт proto/device_control (TurnOn/TurnOff/SetLevel),
общий Go-модуль proto/ для переиспользования сгенерированного кода.
device-control-service принимает команды по gRPC, обновляет desired_state
в Redis и публикует их в MQTT; слушает devices/+/telemetry и devices/+/ack
для отметки живости устройства и обновления reported_state; горутина
health-check переводит устройство в offline по таймауту и публикует
событие в RabbitMQ (device.status_changed) для будущего notification-service.

Проверено сквозным тестом через docker compose: grpcurl TurnOn/SetLevel
меняет desired_state и уходит в MQTT, mosquitto_pub с ack обновляет
reported_state и статус, health-check автоматически переводит устройство
в offline по истечении таймаута.

services/device-control-service/internal/healthcheck/checker.go

@@ -0,0 +1,93 @@
+// Package healthcheck periodically flips devices to offline when they stop
+// sending telemetry/acks, per the platform's Device Shadow health-check
+// design (a goroutine + graceful shutdown, deliberately simple).
+package healthcheck
+
+import (
+	"context"
+	"log/slog"
+	"time"
+)
+
+// DeviceStore is the subset of shadow.Store the checker needs, kept as an
+// interface so tests don't require a real Redis.
+type DeviceStore interface {
+	KnownDevices(ctx context.Context) ([]string, error)
+	MarkOfflineIfStale(ctx context.Context, deviceID string, timeout time.Duration) (bool, error)
+}
+
+// OnOfflineFunc is called once per device that just transitioned to offline.
+type OnOfflineFunc func(deviceID string)
+
+type Checker struct {
+	store     DeviceStore
+	timeout   time.Duration
+	interval  time.Duration
+	onOffline OnOfflineFunc
+	logger    *slog.Logger
+
+	stop chan struct{}
+	done chan struct{}
+}
+
+func New(store DeviceStore, timeout, interval time.Duration, onOffline OnOfflineFunc, logger *slog.Logger) *Checker {
+	return &Checker{
+		store:     store,
+		timeout:   timeout,
+		interval:  interval,
+		onOffline: onOffline,
+		logger:    logger,
+	}
+}
+
+// Start begins the periodic scan loop. Call once.
+func (c *Checker) Start() {
+	c.stop = make(chan struct{})
+	c.done = make(chan struct{})
+	go c.loop()
+}
+
+// Stop signals the loop to exit and waits for it to finish.
+func (c *Checker) Stop() {
+	close(c.stop)
+	<-c.done
+}
+
+func (c *Checker) loop() {
+	defer close(c.done)
+	ticker := time.NewTicker(c.interval)
+	defer ticker.Stop()
+	for {
+		select {
+		case <-ticker.C:
+			c.checkAll()
+		case <-c.stop:
+			return
+		}
+	}
+}
+
+func (c *Checker) checkAll() {
+	ctx, cancel := context.WithTimeout(context.Background(), c.interval)
+	defer cancel()
+
+	ids, err := c.store.KnownDevices(ctx)
+	if err != nil {
+		c.logger.Error("healthcheck: list known devices failed", "error", err)
+		return
+	}
+
+	for _, id := range ids {
+		changed, err := c.store.MarkOfflineIfStale(ctx, id, c.timeout)
+		if err != nil {
+			c.logger.Error("healthcheck: check device failed", "device_id", id, "error", err)
+			continue
+		}
+		if changed {
+			c.logger.Info("device marked offline", "device_id", id)
+			if c.onOffline != nil {
+				c.onOffline(id)
+			}
+		}
+	}
+}