List Agents

curl -H "Authorization: Bearer conv_YOUR_API_KEY" \
  https://api.convosphere.site/api/agents

{
  "agents": [
    {
      "id": "agent_123",
      "name": "Customer Support Bot",
      "description": "Helps customers with support questions",
      "systemPrompt": "You are a helpful support agent...",
      "model": "gpt-4",
      "status": "active",
      "createdAt": "2024-01-15T10:00:00Z",
      "updatedAt": "2024-01-15T10:00:00Z"
    }
  ]
}