- Refactor whatsapp_service.py to accept bridge_url parameter
- whatsapp_bp.py: remove hardcoded tenant_id=11, use g.tenant_id
- whatsapp_bp.py: webhook now accepts ?tenant_id param with fallback
- config_bp.py: add GET/PUT /config/whatsapp endpoints
- Each tenant can now have its own Baileys bridge URL and settings