Merged WhatsApp CLI support with HTTP API server.
Features:
- HTTP API server for CLI-to-bot communication across Docker boundaries
- WhatsApp text + file sending via `lettabot-message send --file photo.jpg`
- Unified multipart endpoint at /api/v1/messages
- Security: timing-safe auth, localhost binding, same-origin CORS
- Bad MAC error handling for WhatsApp encryption renegotiation
Written by Cameron ◯ Letta Code