Fetch and send top Hacker News front-page posts on demand with topic filtering and delightful mood images.

• Responds to user requests like "hn", "hn 10", or "hn health" with N (default 5) front-page posts (excluding crypto), each as an individual 3-line message.
• Supports topic filters: tech (default), health, hacking, life/lifehacks.
• Handles "more" requests using offset to continue from previous results.
• After sending posts, generates and sends a mood image inspired by the topics, with playful Easter eggs.
• Falls back to manual fetching and a default mood image if automated fetching fails.