Push API changes

* Fix item repair cost formula
* Add "RequestUpdateAvailableFreeLoadout" function (WIP)
* Fix item sell formula
* Fix item stack split on sell
* Fix contract progression counting for objectives other than owned items
* Refactor balance into a proper struct
* Separate and update Season 2 and Season 3 data

src/Prospect.Server.Api/Models/Client/FGetUserInventoryResult.cs

@@ -1,5 +1,6 @@
 using System.Text.Json.Serialization;
 using Prospect.Server.Api.Models.Client.Data;
+using Prospect.Server.Api.Models.Data;
 
 namespace Prospect.Server.Api.Models.Client;
 
@@ -17,7 +18,7 @@ public class FGetUserInventoryResult
     /// </summary>
     [JsonPropertyName("VirtualCurrency")]
     [JsonIgnore(Condition = JsonIgnoreCondition.WhenWritingDefault)]
-    public Dictionary<string, int>? VirtualCurrency { get; set; }
+    public PlayerBalance? VirtualCurrency { get; set; }
 
     /// <summary>
     ///     [optional] Array of virtual currency balance(s) belonging to the user.