feat: add GPU-specific fields to marketplace offers and create dedicated GPU marketplace router

- Add GPU fields (model, memory, count, CUDA version, price, region) to MarketplaceOffer model
- Create new marketplace_gpu router for GPU-specific operations
- Update offer sync to populate GPU fields from miner capabilities
- Move GPU attributes from generic attributes dict to dedicated fields
- Update MarketplaceOfferView schema with GPU fields
- Expand CLI README with comprehensive documentation and

cli/miner_gpu_test.py

@@ -10,7 +10,7 @@ import time
 import sys
 
 # Configuration
-DEFAULT_COORDINATOR = "http://localhost:8001"
+DEFAULT_COORDINATOR = "http://localhost:8000"
 DEFAULT_API_KEY = "${MINER_API_KEY}"
 DEFAULT_MINER_ID = "localhost-gpu-miner"