#20685: feat(feishu): add audio/media message support with caption cards

## Summary - Add audio message support for Feishu (playable audio bar instead of file attachment), with automatic duration detection via `music-metadata` - Refactor reply dispatcher to handle media+text payloads: sends media first, then a grey caption card replying to the media message ## Test plan - [ ] Send an audio file (`.mp3`, `.opus`, `.ogg`, etc.) through Feishu and verify it displays as a playable audio bar with correct duration - [ ] Send a message with both text and media, verify media is sent first with a grey caption card following - [ ] Verify fallback: if media send fails, text is delivered normally - [ ] Verify fallback: if caption card fails, text is delivered via plain text 🤖 Generated with [Claude Code](https://claude.com/claude-code)