Add memory

curl --request POST \
  --url https://api.case.dev/memory/v1 \
  --header 'Authorization: Bearer <token>' \
  --header 'Content-Type: application/json' \
  --data '
{
  "messages": [
    {
      "role": "user",
      "content": "Remember that this client prefers conservative investments"
    }
  ],
  "metadata": {
    "client_id": "client_123",
    "matter_id": "matter_456"
  }
}
'

{
  "results": [
    {
      "id": "mem_abc123",
      "memory": "Client prefers conservative investments",
      "event": "ADD"
    }
  ]
}