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.UnitTests/Persistence/ViewerClassDataPersistenceTests.cs

@@ -0,0 +1,54 @@
+using Microsoft.EntityFrameworkCore;
+using Microsoft.Extensions.DependencyInjection;
+using SVSim.Database;
+using SVSim.UnitTests.Infrastructure;
+
+namespace SVSim.UnitTests.Persistence;
+
+public class ViewerClassDataPersistenceTests
+{
+    [Test]
+    public async Task ViewerClassData_round_trips_is_random_leader_skin()
+    {
+        using var factory = new SVSimTestFactory();
+        long viewerId = await factory.SeedViewerAsync();
+
+        using (var seedScope = factory.Services.CreateScope())
+        {
+            var ctx = seedScope.ServiceProvider.GetRequiredService<SVSimDbContext>();
+            var viewer = await ctx.Viewers
+                .Include(v => v.Classes)
+                .FirstAsync(v => v.Id == viewerId);
+            Assert.That(viewer.Classes, Is.Not.Empty, "fresh viewer should have seeded ViewerClassData rows");
+            viewer.Classes[0].IsRandomLeaderSkin = true;
+            await ctx.SaveChangesAsync();
+        }
+
+        using var verifyScope = factory.Services.CreateScope();
+        var ctx2 = verifyScope.ServiceProvider.GetRequiredService<SVSimDbContext>();
+        var viewer2 = await ctx2.Viewers
+            .Include(v => v.Classes)
+            .AsNoTracking()
+            .FirstAsync(v => v.Id == viewerId);
+        Assert.That(viewer2.Classes[0].IsRandomLeaderSkin, Is.True, "flag should round-trip through SaveChanges");
+
+        // Other classes still default to false.
+        Assert.That(viewer2.Classes.Skip(1).All(c => !c.IsRandomLeaderSkin), Is.True);
+    }
+
+    [Test]
+    public async Task ViewerClassData_defaults_is_random_leader_skin_to_false()
+    {
+        using var factory = new SVSimTestFactory();
+        long viewerId = await factory.SeedViewerAsync();
+
+        using var scope = factory.Services.CreateScope();
+        var ctx = scope.ServiceProvider.GetRequiredService<SVSimDbContext>();
+        var viewer = await ctx.Viewers
+            .Include(v => v.Classes)
+            .AsNoTracking()
+            .FirstAsync(v => v.Id == viewerId);
+
+        Assert.That(viewer.Classes.All(c => !c.IsRandomLeaderSkin), Is.True);
+    }
+}