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/domain/marketplace.py

@@ -17,6 +17,13 @@ class MarketplaceOffer(SQLModel, table=True):
     status: str = Field(default="open", max_length=20)
     created_at: datetime = Field(default_factory=datetime.utcnow, nullable=False, index=True)
     attributes: dict = Field(default_factory=dict, sa_column=Column(JSON, nullable=False))
+    # GPU-specific fields
+    gpu_model: Optional[str] = Field(default=None, index=True)
+    gpu_memory_gb: Optional[int] = Field(default=None)
+    gpu_count: Optional[int] = Field(default=1)
+    cuda_version: Optional[str] = Field(default=None)
+    price_per_hour: Optional[float] = Field(default=None)
+    region: Optional[str] = Field(default=None, index=True)
 
 
 class MarketplaceBid(SQLModel, table=True):