Use nav beacon locations for announcements (#26437)

* use nav beacon locations for announcements

* :thumbs_up:

Content.Shared/Pinpointer/NavMapBeaconComponent.cs

@@ -16,6 +16,13 @@ public sealed partial class NavMapBeaconComponent : Component
     [AutoNetworkedField]
     public string? Text;
 
+    /// <summary>
+    /// A localization string that populates <see cref="Text"/> if it is null at mapinit.
+    /// Used so that mappers can still override Text while mapping.
+    /// </summary>
+    [DataField]
+    public LocId? DefaultText;
+
     [ViewVariables(VVAccess.ReadWrite), DataField]
     [AutoNetworkedField]
     public Color Color = Color.Orange;