fix(auth): signal auth_completed when client secrets check fails

Without this signal, the CLI blocks for 5 minutes (timeout) instead of
immediately reporting the missing credentials error.

Closes CodeRabbit review on PR taylorwilsdon#505.

Author: Milofax

auth/oauth_callback_server.py

@@ -82,6 +82,8 @@ async def oauth_callback(request: Request):
                 # Check if we have credentials available (environment variables or file)
                 error_message = check_client_secrets()
                 if error_message:
+                    self.auth_result = {"success": False, "user_id": None, "error": error_message}
+                    self.auth_completed.set()
                     return create_server_error_response(error_message)
 
                 logger.info(