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.

migrations/004_create_popup_ads_table.sql

@@ -0,0 +1,15 @@
+CREATE TABLE IF NOT EXISTS popup_ads (
+    id UUID PRIMARY KEY,
+    user_id UUID NOT NULL REFERENCES "user"(id) ON DELETE CASCADE,
+    type VARCHAR(20) NOT NULL,
+    label TEXT NOT NULL,
+    value TEXT NOT NULL,
+    is_active BOOLEAN NOT NULL DEFAULT TRUE,
+    max_triggers_per_session INTEGER NOT NULL DEFAULT 3,
+    created_at TIMESTAMPTZ DEFAULT CURRENT_TIMESTAMP,
+    updated_at TIMESTAMPTZ,
+    version BIGINT NOT NULL DEFAULT 1
+);
+
+CREATE INDEX IF NOT EXISTS idx_popup_ads_user_id ON popup_ads(user_id);
+CREATE INDEX IF NOT EXISTS idx_popup_ads_user_active ON popup_ads(user_id, is_active);