fix import for oauth2.py

Author: yannj-fr

src/mcp/client/auth/__init__.py

@@ -4,4 +4,22 @@
 Implements authorization code flow with PKCE and automatic token refresh.
 """
 
-from mcp.client.auth.oauth2 import *  # noqa: F403
+from mcp.client.auth.oauth2 import (
+    OAuthClientProvider,
+    OAuthContext,
+    OAuthFlowError,
+    OAuthRegistrationError,
+    OAuthTokenError,
+    PKCEParameters,
+    TokenStorage,
+)
+
+__all__ = [
+    "OAuthClientProvider",
+    "OAuthContext",
+    "OAuthFlowError",
+    "OAuthRegistrationError",
+    "OAuthTokenError",
+    "PKCEParameters",
+    "TokenStorage",
+]