List DM conversations

curl --request GET \
  --url https://api.smartlyq.com/v1/social/conversations \
  --header 'Authorization: Bearer <token>'

{
  "success": true,
  "data": {
    "conversations": [
      {
        "id": 101,
        "social_account_id": 789,
        "platform": "facebook",
        "participant_name": "Alice",
        "participant_avatar": null,
        "snippet": "Hi, a question…",
        "unread_count": 2,
        "last_message_at": "2026-03-01 15:45:00",
        "status": "open",
        "meta_window_open": true
      }
    ]
  },
  "pagination": {
    "page": 1,
    "per_page": 20,
    "total": 1
  },
  "meta": {
    "request_id": "req_abc123",
    "timestamp": "2026-03-01T16:00:00Z"
  }
}