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

apps/coordinator-api/src/app/schemas.py

@@ -190,6 +190,12 @@ class MarketplaceOfferView(BaseModel):
     sla: str
     status: str
     created_at: datetime
+    gpu_model: Optional[str] = None
+    gpu_memory_gb: Optional[int] = None
+    gpu_count: Optional[int] = 1
+    cuda_version: Optional[str] = None
+    price_per_hour: Optional[float] = None
+    region: Optional[str] = None
 
 
 class MarketplaceStatsView(BaseModel):