fix(lint): fix import order in card_resolver.py (I001)

Move pydantic import to correct position per project isort config

Author: amit-raut

src/a2a/client/card_resolver.py

@@ -6,6 +6,8 @@
 
 import httpx
 
+from pydantic import ValidationError
+
 from a2a.client.errors import (
     A2AClientHTTPError,
     A2AClientJSONError,
@@ -18,7 +20,6 @@
     A2ASSRFValidationError,
     validate_agent_card_url,
 )
-from pydantic import ValidationError
 
 
 logger = logging.getLogger(__name__)