feat: add provider selection and provider-based AMQP routing - #8

Summary

• allow sessions to specify provider (baileys, whatsmeow, or forwarder)
• publish outgoing messages using provider-based AMQP exchange
• expose provider in session endpoints and auto-connect
• delegate connect/disconnect/reload/qr commands to Whatsmeow adapter when provider is whatsmeow
• fix session command routes by separating reloader service from handler method
• consume provider-specific outgoing queue so Baileys messages are delivered
• consume Baileys routing queue in broker to forward messages from outgoing.baileys

Testing

• npm test

https://chatgpt.com/codex/tasks/task_e_68bb693305f48324bf115c2669e2232a