feat: Admin notifications for incidents, maintenance and announcements

[rafaelrsantosti]

Description

Allow administrators to send notifications to users about incidents, scheduled maintenance, or general announcements.

Features

• Admin can create notifications with a title and message
• Notifications can have different types: incident, maintenance, info
• Notifications appear as a banner or toast for all users
• Users can dismiss notifications they have read
• Admin can set notification priority (normal, high, critical)
• Optional: schedule notifications for future display

Use Cases

• Inform users about scheduled maintenance windows
• Alert users about ongoing incidents affecting the platform
• Announce new features or changes
• Communicate important security updates

Acceptance Criteria

• Admin can create, edit, and delete notifications
• Notifications are visible to all users when active
• Different visual styles for incident/maintenance/info
• Users can dismiss notifications
• Notification history is available