[Epic 7.4] Implement trading safety: EnableLiveTrading flag

[ooples]

User Story

As a trader, I want live trading disabled by default so that I don't accidentally execute real trades.

Acceptance Criteria

• TradeExecutionOptions.EnableLiveTrading default = false
• All adapters check this flag before submitting real orders
• Clear warning logged when live trading is enabled
• Require explicit opt-in: EnableLiveTrading = true
• Paper trading always allowed regardless of flag
• Exception thrown if live trade attempted without flag

Safety Layers

1. Adapter level: UsePaper = true (broker-specific)
2. Global level: EnableLiveTrading = false (library-wide)
3. Confirmation: Optional confirmation callback before orders

Usage

.ConfigureAutoTrading(trade => {
    // This will throw if EnableLiveTrading is false
    trade.Alpaca(new AlpacaOptions { UsePaper = false })
        .OnSignal(buySignal)
        .MarketBuy(quantity: 10);
}, new TradeExecutionOptions {
    EnableLiveTrading = true,  // Explicit opt-in required
    ConfirmBeforeOrder = true  // Optional extra safety
});

Dependencies

• [Epic 7.1] Define IAutoTradeAdapter interface