DeepSeek retires deepseek-chat and deepseek-reasoner API aliases today

DeepSeek's legacy model aliases deepseek-chat and deepseek-reasoner stopped responding at 15:59 UTC today, requiring all developers to update integrations to deepseek-v4-flash or deepseek-v4-pro. The migration keeps the same base URL and API key but must be in place before the hard cutoff or API calls return errors.