Price orders at the provider's real trade rate instead of the mid quote.

montzar_live_price is the midpoint between the colleague's buy and sell rates,
so orders priced straight from it charged the customer less than we pay the
provider and the whole spread was lost on every trade, even though the app
already showed the correct side. Order base price now follows the traded side
(base + spread on buy, base - spread on sell), which also makes price_original
the real cost basis so the dashboard stops counting the provider spread as
profit. Conditional order triggers compare against the same displayed price.

Co-authored-by: Cursor <cursoragent@cursor.com>

app/Services/ConfigService.php

@@ -132,6 +132,22 @@ class ConfigService
         return $this->displayBuyPriceDiffRial();
     }
 
+    /**
+     * اختلاف دوطرفهٔ نرخ همکار (نصف فاصلهٔ نرخ خرید و فروش همکار).
+     *
+     * پایهٔ ذخیره‌شده (montzar_live_price) وسط این دو نرخ است، پس نرخ واقعی معاملهٔ ما با همکار
+     * «پایه + این مقدار» برای خرید و «پایه − این مقدار» برای فروش است.
+     * فقط برای provider همکار معنا دارد؛ بقیه نرخ دوطرفه نمی‌دهند.
+     */
+    public function providerTradeSpreadRial(): float
+    {
+        if ($this->priceProvider() !== 'montzar') {
+            return 0.0;
+        }
+
+        return max(0.0, (float) $this->get('montzar_diff', 0));
+    }
+
     /** درصد کارمزد سفارش — fee_service_charge_percentage، service_charge_percentage، config/fee.php */
     public function orderServiceChargePercentage(): float
     {