feat: add notification events handling and MQTT integration

- Implemented notification event publishing with a new NotificationEventPublisher interface.
- Created a noopNotificationEventPublisher for testing purposes.
- Added functionality to publish notification created events via MQTT.
- Introduced a new stream event publisher for handling job logs and updates.
- Added database migration for popup_ads table.
- Created tests for notification events and popup ads functionality.
- Established MQTT connection and publishing helpers for event messages.

internal/transport/mqtt/bootstrap.go

@@ -0,0 +1,41 @@
+package mqtt
+
+import (
+	"context"
+
+	pahomqtt "github.com/eclipse/paho.mqtt.golang"
+	"stream.api/internal/dto"
+	"stream.api/internal/service"
+	"stream.api/pkg/logger"
+)
+
+type MQTTBootstrap struct{ *streamEventPublisher }
+
+func NewMQTTBootstrap(jobService *service.JobService, agentRT agentRuntime, appLogger logger.Logger) (*MQTTBootstrap, error) {
+	publisher, err := newStreamEventPublisher(jobService, agentRT, appLogger)
+	if err != nil {
+		return nil, err
+	}
+	return &MQTTBootstrap{streamEventPublisher: publisher}, nil
+}
+
+func (b *MQTTBootstrap) Start(ctx context.Context) {
+	if b == nil || b.streamEventPublisher == nil {
+		return
+	}
+	b.streamEventPublisher.start(ctx)
+}
+
+func (b *MQTTBootstrap) Client() pahomqtt.Client {
+	if b == nil || b.streamEventPublisher == nil {
+		return nil
+	}
+	return b.client
+}
+
+func PublishAgentMQTTEvent(client pahomqtt.Client, appLogger logger.Logger, eventType string, agent *dto.AgentWithStats) {
+	publishMQTTEvent(client, appLogger, defaultMQTTPrefix, mqttEvent{
+		Type:    eventType,
+		Payload: mapAgentPayload(agent),
+	})
+}