refactor: migrate recurrent and monitoring services to PricingEngine

Mechanical re-point of calculate_renewal_price calls to use unified
PricingEngine. Both services now get consistent pricing with correct
discount formulas and server fallback behavior.

app/services/monitoring_service.py

@@ -1053,12 +1053,13 @@ class MonitoringService:
                     autopay_period = 30
 
                 try:
-                    renewal_cost = await self.subscription_service.calculate_renewal_price(
-                        subscription,
-                        autopay_period,
-                        db,
-                        user=user,
+                    from app.services.pricing_engine import PricingEngine
+
+                    pricing_engine = PricingEngine()
+                    pricing = await pricing_engine.calculate_renewal_price(
+                        db, subscription, autopay_period, user=user,
                     )
+                    renewal_cost = pricing.final_total
                 except Exception as e:
                     logger.error(
                         'Ошибка расчёта стоимости автопродления, пропускаем',

app/services/recurrent_payment_service.py

@@ -224,12 +224,13 @@ async def _process_single_subscription(
         autopay_period = 30
 
     try:
-        renewal_cost = await subscription_service.calculate_renewal_price(
-            subscription,
-            autopay_period,
-            db,
-            user=user,
+        from app.services.pricing_engine import PricingEngine
+
+        pricing_engine = PricingEngine()
+        pricing = await pricing_engine.calculate_renewal_price(
+            db, subscription, autopay_period, user=user,
         )
+        renewal_cost = pricing.final_total
     except Exception as e:
         logger.error(
             'Ошибка расчёта стоимости для рекуррентного платежа',