Add custom notification threshold settings on Web Dashboard

[mx57]

Добавлена возможность настройки минимального порога размера сделки в USDT для воспроизведения звуковых оповещений и показа всплывающих toast-уведомлений на Web Dashboard. Настройка сохраняется в localStorage и синхронизируется между разделами интерфейса через пользовательские события. Завершена задача web-dashboard-custom-alerts в agent_tasks.json.

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PR created automatically by Jules for task 15964371833376104132 started by @mx57

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