fix(viewer): default ClassExp.Level to 1 for new viewers

Client RankMatchUI.onOpen indexes _classCharaExpList[level - 1]
unconditionally; level 0 (the prior default) throws IOOR.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

SVSim.Database/Repositories/Viewer/ViewerRepository.cs

@@ -272,7 +272,9 @@ public class ViewerRepository : IViewerRepository
             {
                 Class = ce,
                 Exp = 0,
-                Level = 0,
+                // Client unconditionally indexes `_classCharaExpList[level - 1]` in
+                // RankMatchUI.onOpen → CharacterExps.GetClassCharacterExps; level 0 throws IOOR.
+                Level = 1,
                 LeaderSkin = skin ?? new LeaderSkinEntry { Id = 0, Name = "<missing>", ClassId = ce.Id }
             };
         }).ToList();