Upgrade the Feishu channel from basic text-only to full feature parity with
Telegram/Discord: interactive card messages with markdown rendering, message
editing (MessageEditor), placeholder messages (PlaceholderCapable), emoji
reactions (ReactionCapable), and inbound/outbound media support (MediaSender).
Also add @mention detection with lazy bot open_id discovery, group trigger
filtering with mention awareness, and multi-type inbound message parsing
(text, post, image, file, audio, video).
c9fb681f3b