Add fleet alert notifications for shop floor PCs

Fleet alerts push server notifications to endpoint PCs via the command pipe.
Operators acknowledge alerts via toast UI in the tray. Backend tracks
acknowledgements per asset to prevent re-showing dismissed alerts.

Backend: alertfleet/alertscope/alerttimeout columns, GET/POST /api/endpoints/alerts,
NotificationAcknowledgement model with unique constraint, hostname validation.

Frontend: Alert Fleet checkbox in notification form.

Agent: FleetAlertClient polls alerts, FleetAlertStore tracks acknowledged IDs,
FleetAlertForm displays toast (no auto-dismiss), FleetAlertWorker 60s polling.

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

plugins/notifications/models/notification.py

@@ -146,6 +146,9 @@ class Notification(db.Model):
     # ~11 people are listed.
     employeesso = db.Column(db.Text, nullable=True)
     employeename = db.Column(db.Text, nullable=True)
+    alertfleet = db.Column(db.Boolean, default=False)
+    alertscope = db.Column(db.JSON, nullable=True)
+    alerttimeout = db.Column(db.Integer, nullable=True)
 
     # Relationships
     notificationtype = db.relationship('NotificationType', backref='notifications')
@@ -194,7 +197,10 @@ class Notification(db.Model):
             'isshopfloor': bool(self.isshopfloor) if self.isshopfloor is not None else False,
             'employeesso': self.employeesso,
             'employeename': self.employeename,
-            'iscurrent': self.is_current
+            'iscurrent': self.is_current,
+            'alertfleet': bool(self.alertfleet) if self.alertfleet is not None else False,
+            'alertscope': self.alertscope,
+            'alerttimeout': self.alerttimeout
         }
 
         # Add type info