feat(viewer): add ViewerClassData.IsRandomLeaderSkin column

Adds the bool column (defaults false) to the [Owned] ViewerClassData
entity and a two-test persistence suite that verifies round-trip and
default-value behaviour via SQLite/EnsureCreated.

SVSim.Database/Models/ViewerClassData.cs

@@ -7,7 +7,14 @@ public class ViewerClassData
 {
     public int Level { get; set; }
     public int Exp { get; set; }
-    
+
+    /// <summary>
+    /// Per-class "use random leader skin from owned pool" preference. Defaults to false.
+    /// No client-side setter exists today (only per-deck random-leader-skin endpoints exist);
+    /// persisted now so when/if a class-level toggle is discovered, the write target exists.
+    /// </summary>
+    public bool IsRandomLeaderSkin { get; set; }
+
     #region Navigation Properties
 
     public ClassEntry Class { get; set; } = new ClassEntry();