[rfprod]

• bump version to 0.4.0;
• add rag and skip_embedding parameters to argument functions and CLI;
• implement streaming mode for print() and print_message();
• update loop increment style for consistency;
• replace printf calls with UserInterface and remove emoji from messages;
• rename config to ollama_config for clarity;
• add retrieving_utils with RetrievingUtils class and RetrievingUtilsConfig;
• implement retrieve(), generate_answer(), and run() methods in RetrievingUtils;
• initialize RetrievingUtils in RAG execution path;
• add get_config_value and get_url_value getter methods to clients;
• refactor streaming with callback-based approach for HTTP and LLM;
• add fetch_web_content_stream and curl_streaming_write_callback;
• add WebContentStream struct and process_chunk for JSON buffering and parsing;
• convert WriteCallback to member function curl_write_callback for streaming;
• move process_response to public section of OllamaClient;
• refactor process_response_stream to accept const reference;
• improve variable declaration ordering and extract inline map initialization;
• improve control flow with else-if pattern;