feat: add campaign alerts feature with alerts management and UI integration

- Introduced a new `CampaignAlerts` class for handling alerts logic.
- Added database migration for `campaign_alerts` table creation.
- Implemented methods for fetching, marking, and deleting alerts in the `CampaignAlerts` factory class.
- Created a new view for displaying campaign alerts with filtering options.
- Updated the main client view to include a badge for the number of alerts.
- Enhanced sync functionality to support campaigns and products separately.
- Adjusted styles for alert badges in the UI.

migrations/015_campaign_alerts_unseen.sql

@@ -0,0 +1,7 @@
+-- Migracja: flaga unseen dla alertow kampanii
+-- Opis: nowe alerty sa unseen=1, po wejsciu na strone alertow oznaczane jako unseen=0
+
+ALTER TABLE `campaign_alerts`
+  ADD COLUMN IF NOT EXISTS `unseen` TINYINT(1) NOT NULL DEFAULT 1 AFTER `meta_json`;
+
+CREATE INDEX IF NOT EXISTS `idx_alert_unseen` ON `campaign_alerts` (`unseen`);