fix: catch error in subscription, propagate it to the main file

internal/app/bridge/app.go

@@ -52,7 +52,11 @@ func New(cfg *config.Config) (*BridgeApp, error) {
 		cleanup()
 		return nil, err
 	}
-	mqttClient.Subscribe()
+
+	if err := mqttClient.Subscribe(); err != nil {
+		cleanup()
+		return nil, err
+	}
 
 	return &BridgeApp{
 		Cfg:          cfg,

internal/pkg/bridge/mqtt.go

@@ -48,10 +48,14 @@ func NewMQTTClient(cfg *config.Config, publishHandler func(mqtt.Message)) (*MQTT
 }
 
 // Subscribe subscribes to the default bridge topic.
-func (m *MQTTClient) Subscribe() {
+func (m *MQTTClient) Subscribe() error {
 	token := m.Client.Subscribe(subscribeTopic, 1, nil)
 	token.Wait()
+	if err := token.Error(); err != nil {
+		return fmt.Errorf("mqtt subscribe: %w", err)
+	}
 	slog.Info("MQTT subscribed", "topic", subscribeTopic)
+	return nil
 }
 
 // Disconnect disconnects the client with quiesce.