Fix list inv desync upon inserting stackables (cosmatic-drift-14#188)

Fixes a desync upon inserting a stack into a container that already had
a stack of the same item type. This was because UpdateUI was only being
called server side which has no effect.

Content.Server/Item/ItemSystem.cs

@@ -19,6 +19,5 @@ protected override void OnStackCountChanged(EntityUid uid, ItemComponent compone
             return;
 
         _storage.RecalculateStorageUsed(container.Owner, storage);
-        _storage.UpdateUI(container.Owner, storage);
     }
 }

Content.Shared/Item/SharedItemSystem.cs

@@ -6,6 +6,7 @@
 using Content.Shared.Examine;
 using Content.Shared.Item.ItemToggle.Components;
 using Content.Shared.Storage;
+using Content.Shared.Storage.EntitySystems;
 using JetBrains.Annotations;
 using Robust.Shared.Containers;
 using Robust.Shared.GameStates;
@@ -21,6 +22,9 @@ public abstract class SharedItemSystem : EntitySystem
     [Dependency] private   readonly SharedCombatModeSystem _combatMode = default!;
     [Dependency] protected readonly SharedContainerSystem Container = default!;
 
+    // CD: Fix stackable insert desync
+    [Dependency] private readonly SharedStorageSystem _storage = default!;
+
     public override void Initialize()
     {
         base.Initialize();
@@ -99,8 +103,15 @@ protected virtual void OnStackCountChanged(EntityUid uid, ItemComponent componen
             return;
 
         SetSize(uid, args.NewCount * size, component);
+
+        // CD: Fix stackable insert desync
+        if (!Container.TryGetContainingContainer(uid, out var container) ||
+            !TryComp<StorageComponent>(container.Owner, out var storage))
+            return;
+        _storage.UpdateUI(container.Owner, storage);
+        // end CD
     }
-    
+
     private void AddPickupVerb(EntityUid uid, ItemComponent component, GetVerbsEvent<InteractionVerb> args)
     {
         if (args.Hands == null ||