Rework wheelchairbound (#24173)

* Rework wheelchairbound

Fixes the save/load bug and fixes it being a singleton.

* weh

Content.Server/Traits/Assorted/BuckleOnMapInitSystem.cs

@@ -0,0 +1,19 @@
+using Content.Shared.Buckle;
+
+namespace Content.Server.Traits.Assorted;
+
+public sealed class BuckleOnMapInitSystem : EntitySystem
+{
+    [Dependency] private readonly SharedBuckleSystem _buckleSystem = default!;
+
+    public override void Initialize()
+    {
+        SubscribeLocalEvent<BuckleOnMapInitComponent, MapInitEvent>(OnMapInit);
+    }
+
+    private void OnMapInit(EntityUid uid, BuckleOnMapInitComponent component, MapInitEvent args)
+    {
+        var buckle = Spawn(component.Prototype, Transform(uid).Coordinates);
+        _buckleSystem.TryBuckle(uid, uid, buckle);
+    }
+}