Retrieves raw news articles from the database, allowing the client (LLM) to summarize them. Takes optional category (string) and limit (integer, default 20) arguments. Returns a list of article dictionaries, each containing id, title, link, published, source, and content. Available categories: tech, data_science, llm_tools, cybersecurity, linux, audio_dsp, startups, news, science, research, policy.