- Add POST /marketplace/gpu/{gpu_id}/confirm endpoint for client booking acknowledgment
- Add POST /tasks/ollama endpoint for Ollama task submission with model and prompt parameters
- Add POST /payments/send endpoint as stub for blockchain payment processing
- Add GPUConfirmRequest, OllamaTaskRequest, and PaymentRequest models
- Add CLI commands: confirm, ollama-task, and pay for new endpoints
- Include validation
