Get Chat History

{
  "id": "chat_abc123",
  "title": "Support Chat",
  "messages": [
    {
      "id": "msg_1",
      "role": "user",
      "content": "How do I reset my password?",
      "created_at": "2025-01-15T10:30:00Z"
    },
    {
      "id": "msg_2",
      "role": "assistant",
      "content": "To reset your password...",
      "sources": [],
      "created_at": "2025-01-15T10:30:01Z"
    }
  ]
}