Retrieves a list of all call batches for the authenticated user.
GET /api/v1/batch/list
GET
[ { "batchId": "batch_123...", "status": "processing", "total": 1000, "processed": 500, "succeeded": 450, "failed": 50, "percentComplete": 50, "createdAt": "2024-01-15T10:00:00.000Z", "agentId": "agent_abc...", "priority": 5 } ]