Add Feishu

Adds Feishu (Lark) as a messaging channel to NanoClaw using WebSocket long connections instead of webhooks, so you don't need to expose a public URL. The bot responds to every message without requiring @mentions or trigger words. Setup involves running the skills engine to deterministically merge channel support into your codebase, creating a Feishu app with the right event subscriptions and permissions, then registering your chat in SQLite. The implementation is straightforward if you're already running NanoClaw and want Chinese enterprise messaging support, though you'll need to navigate Feishu's Open Platform to get credentials and publish your app before events flow through.