feat(battle-xp): IBattleXpService with per-mode overrides and auto level-up

- IBattleXpService.GrantAsync mutates viewer.Classes in place; caller SaveChanges
- Resolves win/loss amount from per-mode override or global XpPerWin/XpPerLoss
- Story mode ignores isWin, uses StoryXpPerClear ?? XpPerWin
- Level-up loop consults curve[row.Level].NecessaryExp; carries overflow
- Saturates at max curve level (excess piles in Exp)
- Unknown classId → no-op returning (0, 0, 1), logs Warning
- 10 unit tests (Moq-backed curve stub); DI registered next to InventoryService
- GameConfigurationJsonbTests baseline updated (19 sections)

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

SVSim.EmulatedEntrypoint/Program.cs

@@ -99,6 +99,8 @@ public class Program
         builder.Services.AddScoped<IGachaPointService, GachaPointService>();
         builder.Services.AddScoped<SVSim.Database.Services.Inventory.IInventoryService,
                                   SVSim.Database.Services.Inventory.InventoryService>();
+        builder.Services.AddScoped<SVSim.Database.Services.BattleXp.IBattleXpService,
+                                  SVSim.Database.Services.BattleXp.BattleXpService>();
         builder.Services.AddScoped<SVSim.Database.Repositories.BattlePass.IBattlePassRepository,
                                     SVSim.Database.Repositories.BattlePass.BattlePassRepository>();
         builder.Services.AddScoped<SVSim.Database.Repositories.BattlePass.IViewerBattlePassRepository,