List Conversations

{
  "success": true,
  "data": [
    {
      "id": "conversation-uuid",
      "lead": {
        "id": "lead-uuid",
        "name": "John Smith",
        "phone": "+15551234567"
      },
      "last_message": {
        "content": "Thanks for the information!",
        "role": "user",
        "timestamp": "2024-01-15T14:30:00Z"
      },
      "unread_count": 2,
      "status": "active",
      "updated_at": "2024-01-15T14:30:00Z"
    }
  ],
  "pagination": {
    "total": 85,
    "limit": 50,
    "offset": 0,
    "has_more": true
  }
}