Implement balance update callback in TradingBotBase for immediate sync

- Removed the private _currentBalance field and replaced it with direct access to Config.BotTradingBalance.
- Added OnBalanceUpdatedCallback to TradingBotBase for immediate synchronization and database saving when the balance is updated.
- Updated LiveTradingBotGrain to set the callback for balance updates, ensuring accurate state management.
- Modified PostgreSqlBotRepository to save the updated bot trading balance during entity updates.

src/Managing.Infrastructure.Database/PostgreSql/PostgreSqlBotRepository.cs

@@ -83,6 +83,7 @@ public class PostgreSqlBotRepository : IBotRepository
         existingEntity.AccumulatedRunTimeSeconds = bot.AccumulatedRunTimeSeconds;
         existingEntity.MasterBotUserId =
             bot.MasterBotUserId ?? existingEntity.MasterBotUserId;
+        existingEntity.BotTradingBalance = bot.BotTradingBalance;
 
         await _context.SaveChangesAsync().ConfigureAwait(false);
     }