Fix entity-specific component states networking (#7410)

Content.Server/Alert/ServerAlertsSystem.cs

@@ -1,7 +1,19 @@
 using Content.Shared.Alert;
+using Robust.Server.GameObjects;
 
 namespace Content.Server.Alert;
 
-// The only reason this exists is because the DI system requires the shared AlertsSystem
-// to be abstract.
-internal sealed class ServerAlertsSystem : AlertsSystem { }
+internal sealed class ServerAlertsSystem : AlertsSystem
+{
+    public override void Initialize()
+    {
+        base.Initialize();
+
+        SubscribeLocalEvent<AlertsComponent, PlayerAttachedEvent>(OnPlayerAttached);
+    }
+
+    private void OnPlayerAttached(EntityUid uid, AlertsComponent component, PlayerAttachedEvent args)
+    {
+        Dirty(component);
+    }
+}