Update transfer_to_phone tool configuration

Update configuration for the transfer_to_phone tool.

Allows you to configure:
- Enable/disable the tool
- Phone destinations (list of phone numbers with names and availability)
- Transfer message

Phone destinations structure:
```json
{
  "phone_number": "+393471234567",  // E.164 format
  "name": "Reception",
  "description": "Main reception desk",
  "available_hours": {  // Optional schedule
    "monday": ["09:00 - 18:00"],
    ...
  }
}
```

Important:
- phone_destinations is REQUIRED when enabling the tool (is_enabled=true)
- Phone numbers must be in E.164 format
- Phone numbers must be unique within destinations
- This tool is mutually exclusive with transfer_to_mobile_operator

Authentication:
- API key with READ_WRITE permission