feat: implement backend API clients for multi-marketplace integration and frontend service layer

backend/mega_api/services/assortment.py

@@ -0,0 +1,32 @@
+from typing import Dict, Any, List
+from ..client import MegaClient
+
+class AssortmentService:
+    """Service to handle MegaMarket Assortment/Prices/Stocks."""
+    
+    def __init__(self, client: MegaClient):
+        self.client = client
+
+    def update_stocks(self, stocks: List[Dict[str, Any]]) -> Dict[str, Any]:
+        """
+        Обновить остатки.
+        Endpoint: /stockService/stock/update
+        """
+        payload = {
+            "data": {
+                "stocks": stocks
+            }
+        }
+        return self.client.post("/stockService/stock/update", data=payload)
+
+    def update_prices(self, prices: List[Dict[str, Any]]) -> Dict[str, Any]:
+        """
+        Обновить цены.
+        Endpoint: /priceService/price/update
+        """
+        payload = {
+            "data": {
+                "prices": prices
+            }
+        }
+        return self.client.post("/priceService/price/update", data=payload)

backend/mega_api/services/orders.py

@@ -0,0 +1,55 @@
+from typing import Dict, Any, List
+from ..client import MegaClient
+
+class OrdersService:
+    """Service to handle MegaMarket Orders (FBS)."""
+    
+    def __init__(self, client: MegaClient):
+        self.client = client
+
+    def get_new_orders(self, limit: int = 100) -> Dict[str, Any]:
+        """
+        Мегамаркет обычно отправляет заказы webhook-ами, но также имеет методы пулинга или запроса списков.
+        Endpoint: /orderService/order/search (условно)
+        """
+        payload = {
+            "data": {
+                "statuses": ["NEW"],
+                "limit": limit
+            }
+        }
+        return self.client.post("/orderService/order/search", data=payload)
+
+    def confirm_order(self, order_id: str, items: List[Dict[str, Any]]) -> Dict[str, Any]:
+        """
+        Подтвердить заказ (отправить информацию о том, что он принят в работу).
+        Endpoint: /orderService/order/confirm
+        """
+        payload = {
+            "data": {
+                "shipments": [
+                    {
+                        "shipmentId": order_id,
+                        "items": items
+                    }
+                ]
+            }
+        }
+        return self.client.post("/orderService/order/confirm", data=payload)
+
+    def reject_order(self, order_id: str, reason: str) -> Dict[str, Any]:
+        """
+        Отменить заказ.
+        Endpoint: /orderService/order/reject
+        """
+        payload = {
+            "data": {
+                "shipments": [
+                    {
+                        "shipmentId": order_id,
+                        "reason": {"type": reason}
+                    }
+                ]
+            }
+        }
+        return self.client.post("/orderService/order/reject", data=payload)