[MERCURE] Add notification handler and update modal title on notifications event

[ViniTou]

🎫 Issue	IBX-XXXXX

Description:

• Decoupled Notification Polling: Refactored admin.notifications.modal.js to skip the default 30s polling loop if an external notification handler (like Mercure) is detected via a meta tag.
• Standardized Update Event: Added a global listener for ibexa-notifications:update on document.body. This allows external handlers to push updated pending and total counts directly into the UI.
• Automatic Refresh: Integrated the new update event with existing internal methods (setPendingNotificationCount and updateModalTitleTotalInfo) to ensure the notice dot and notification list refresh automatically when an update is pushed.
• New Twig Component Group: Added the admin-ui-notification-handler group to the main layout, providing a clean entry point for other bundles to inject notification-related logic without hacking existing scripts.

This way I could get rid of that ugly hacking with HUGE new interval that was disabling old pooling from outside admin-ui bundle.

For QA:

Just check if notifcations are working as always.

Documentation:

[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud