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

backend/lamoda_api/__init__.py

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+from .client import LamodaClient
+from .services.products import ProductsService
+from .services.orders import OrdersService
+
+class LamodaAPI:
+    """
+    Main entry point for Lamoda Seller Partner SDK.
+    Instantiates all services with a shared client.
+    """
+    def __init__(self, api_key: str = None):
+        self.client = LamodaClient(api_key)
+        
+        # Initialize services
+        self.products = ProductsService(self.client)
+        self.orders = OrdersService(self.client)

backend/lamoda_api/client.py

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+import os
+import requests
+import time
+from typing import Dict, Any, Optional
+from .exceptions import LamodaAPIError, LamodaAuthError, LamodaRateLimitError, LamodaBadRequestError, LamodaNotFoundError
+
+class LamodaClient:
+    """Base client for interacting with Lamoda Seller Partner API."""
+    
+    BASE_URL = "https://api.seller.lamoda.ru"
+    
+    def __init__(self, api_key: Optional[str] = None):
+        # Fetch from env if not provided
+        self.api_key = api_key or os.getenv('LAMODA_API_KEY')
+        
+        if not self.api_key:
+            raise ValueError("LAMODA_API_KEY must be provided")
+            
+        self.session = requests.Session()
+        # Lamoda often uses X-API-Key or Authorization Bearer depending on the endpoint.
+        # We assume X-API-Key as the standard for B2B API integrations.
+        self.session.headers.update({
+            "X-API-Key": self.api_key,
+            "Content-Type": "application/json"
+        })
+
+    def request(self, method: str, path: str, data: Optional[Dict[str, Any]] = None, params: Optional[Dict[str, Any]] = None, retries: int = 3) -> Dict[str, Any]:
+        """Perform HTTP request to Lamoda API with automatic retries."""
+        url = f"{self.BASE_URL}{path}"
+        
+        for attempt in range(retries):
+            try:
+                response = self.session.request(method, url, json=data, params=params)
+                
+                # Check rate limiting
+                if response.status_code == 429:
+                    if attempt < retries - 1:
+                        time.sleep(2 ** attempt)  # Exponential backoff
+                        continue
+                    raise LamodaRateLimitError("Rate limit exceeded")
+
+                if response.status_code in (401, 403):
+                    raise LamodaAuthError(f"Authentication failed: {response.text}")
+                    
+                if response.status_code == 400:
+                    raise LamodaBadRequestError(f"Bad Request: {response.text}")
+
+                if response.status_code == 404:
+                    raise LamodaNotFoundError(f"Not Found: {response.text}")
+                    
+                response.raise_for_status()
+                
+                if response.content:
+                    return response.json()
+                return {}
+
+            except requests.exceptions.RequestException as e:
+                if attempt < retries - 1:
+                    time.sleep(2 ** attempt)
+                    continue
+                raise LamodaAPIError(f"Request failed: {str(e)}")
+                
+        raise LamodaAPIError("Request failed after max retries")
+
+    def post(self, path: str, data: Optional[Dict[str, Any]] = None) -> Dict[str, Any]:
+        return self.request("POST", path, data=data)
+
+    def get(self, path: str, params: Optional[Dict[str, Any]] = None) -> Dict[str, Any]:
+        return self.request("GET", path, params=params)
+
+    def put(self, path: str, data: Optional[Dict[str, Any]] = None) -> Dict[str, Any]:
+        return self.request("PUT", path, data=data)

backend/lamoda_api/exceptions.py

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+class LamodaAPIError(Exception):
+    """Base exception for all Lamoda API errors."""
+    pass
+
+class LamodaAuthError(LamodaAPIError):
+    """Raised when authentication fails (HTTP 401 or 403)."""
+    pass
+
+class LamodaRateLimitError(LamodaAPIError):
+    """Raised when API rate limits are exceeded (HTTP 429)."""
+    pass
+
+class LamodaBadRequestError(LamodaAPIError):
+    """Raised when API returns HTTP 400."""
+    pass
+
+class LamodaNotFoundError(LamodaAPIError):
+    """Raised when API returns HTTP 404."""
+    pass

backend/lamoda_api/services/orders.py

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+from typing import Dict, Any, List
+from ..client import LamodaClient
+
+class OrdersService:
+    """Service to handle Lamoda Orders (FBS)."""
+    
+    def __init__(self, client: LamodaClient):
+        self.client = client
+
+    def get_new_orders(self, limit: int = 100) -> Dict[str, Any]:
+        """
+        Get list of new orders (assembly tasks).
+        Endpoint: /v1/orders/new
+        """
+        return self.client.get("/v1/orders/new", params={"limit": limit})
+
+    def confirm_packaging(self, order_ids: List[str]) -> Dict[str, Any]:
+        """
+        Confirm that orders are packaged and ready for dispatch.
+        Endpoint: /v1/orders/pack
+        """
+        return self.client.post("/v1/orders/pack", data={"order_ids": order_ids})

backend/lamoda_api/services/products.py

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+from typing import Dict, Any, List
+from ..client import LamodaClient
+
+class ProductsService:
+    """Service to handle Lamoda Products/Assortment."""
+    
+    def __init__(self, client: LamodaClient):
+        self.client = client
+
+    def get_list(self, limit: int = 100, offset: int = 0, **filters) -> Dict[str, Any]:
+        """
+        Get list of products in the seller's catalog.
+        Endpoint: /v1/products
+        """
+        params = {"limit": limit, "offset": offset}
+        params.update(filters)
+        return self.client.get("/v1/products", params=params)
+
+    def update_stocks(self, items: List[Dict[str, Any]]) -> Dict[str, Any]:
+        """
+        Update stock levels (FBS).
+        Endpoint: /v1/stocks
+        """
+        return self.client.post("/v1/stocks", data={"stocks": items})
+
+    def update_prices(self, items: List[Dict[str, Any]]) -> Dict[str, Any]:
+        """
+        Update prices for products.
+        Endpoint: /v1/prices
+        """
+        return self.client.post("/v1/prices", data={"prices": items})