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

backend/ae_api/__init__.py

@@ -0,0 +1,15 @@
+from .client import AEClient
+from .services.transactions import TransactionsService
+from .services.products import ProductsService
+
+class AliExpressAPI:
+    """
+    Main entry point for AE Platform (AliExpress Russia) SDK.
+    Instantiates all services with a shared client.
+    """
+    def __init__(self, api_token: str = None, user_id: str = None):
+        self.client = AEClient(api_token, user_id)
+        
+        # Initialize services
+        self.transactions = TransactionsService(self.client)
+        self.products = ProductsService(self.client)