feat: add marketplace and AI services RPC endpoints

📋 Marketplace Endpoints:
• GET /marketplace/listings - List all active marketplace items
• POST /marketplace/create - Create new marketplace listing
• Demo listings for GPU and compute resources
• In-memory storage with active status filtering

🤖 AI Services Endpoints:
• POST /ai/submit - Submit AI jobs with payment
• GET /ai/stats - AI service statistics and revenue tracking
• Support for text, image, and training job types

apps/blockchain-node/src/aitbc_chain/rpc/marketplace.py

@@ -0,0 +1,148 @@
+"""Marketplace RPC endpoints for AITBC blockchain"""
+
+from typing import Any, Dict, List, Optional
+from fastapi import HTTPException
+from pydantic import BaseModel, Field
+from datetime import datetime
+
+from ..database import session_scope
+from ..metrics import metrics_registry
+from .router import router
+
+
+class MarketplaceListing(BaseModel):
+    """Marketplace listing model"""
+    listing_id: Optional[str] = None
+    seller_address: str = Field(..., description="Seller wallet address")
+    item_type: str = Field(..., description="Type of item (GPU, compute, etc.)")
+    price: float = Field(..., ge=0, description="Price in AIT")
+    description: str = Field(..., description="Item description")
+    status: str = Field(default="active", description="Listing status")
+    created_at: Optional[datetime] = None
+
+class MarketplaceCreateRequest(BaseModel):
+    """Request to create marketplace listing"""
+    seller_address: str
+    item_type: str
+    price: float
+    description: str
+
+# In-memory storage for demo (in production, use database)
+_marketplace_listings: List[Dict[str, Any]] = [
+    {
+        "listing_id": "demo_001",
+        "seller_address": "ait1demo_seller_123...",
+        "item_type": "GPU",
+        "price": 1000.0,
+        "description": "High-performance NVIDIA RTX 4090 for AI training",
+        "status": "active",
+        "created_at": datetime.now().isoformat()
+    },
+    {
+        "listing_id": "demo_002", 
+        "seller_address": "ait1demo_provider_456...",
+        "item_type": "Compute",
+        "price": 500.0,
+        "description": "10 hours of GPU compute time for deep learning",
+        "status": "active",
+        "created_at": datetime.now().isoformat()
+    }
+]
+
+@router.get("/marketplace/listings", summary="List marketplace items", tags=["marketplace"])
+async def marketplace_listings() -> Dict[str, Any]:
+    """Get all marketplace listings"""
+    try:
+        metrics_registry.increment("rpc_marketplace_listings_total")
+        
+        # Filter active listings
+        active_listings = [listing for listing in _marketplace_listings if listing.get("status") == "active"]
+        
+        return {
+            "listings": active_listings,
+            "total": len(active_listings),
+            "timestamp": datetime.now().isoformat()
+        }
+    except Exception as e:
+        metrics_registry.increment("rpc_marketplace_listings_errors_total")
+        raise HTTPException(status_code=500, detail=str(e))
+
+@router.post("/marketplace/create", summary="Create marketplace listing", tags=["marketplace"])
+async def marketplace_create(request: MarketplaceCreateRequest) -> Dict[str, Any]:
+    """Create a new marketplace listing"""
+    try:
+        metrics_registry.increment("rpc_marketplace_create_total")
+        
+        # Generate unique listing ID
+        listing_id = f"listing_{len(_marketplace_listings) + 1:03d}"
+        
+        # Create new listing
+        new_listing = {
+            "listing_id": listing_id,
+            "seller_address": request.seller_address,
+            "item_type": request.item_type,
+            "price": request.price,
+            "description": request.description,
+            "status": "active",
+            "created_at": datetime.now().isoformat()
+        }
+        
+        # Add to storage
+        _marketplace_listings.append(new_listing)
+        
+        return {
+            "listing_id": listing_id,
+            "status": "created",
+            "message": "Marketplace listing created successfully",
+            "listing": new_listing
+        }
+        
+    except Exception as e:
+        metrics_registry.increment("rpc_marketplace_create_errors_total")
+        raise HTTPException(status_code=500, detail=str(e))
+
+@router.get("/marketplace/listing/{listing_id}", summary="Get marketplace listing by ID", tags=["marketplace"])
+async def marketplace_get_listing(listing_id: str) -> Dict[str, Any]:
+    """Get a specific marketplace listing"""
+    try:
+        metrics_registry.increment("rpc_marketplace_get_total")
+        
+        # Find listing
+        for listing in _marketplace_listings:
+            if listing.get("listing_id") == listing_id:
+                return {
+                    "listing": listing,
+                    "found": True
+                }
+        
+        raise HTTPException(status_code=404, detail="Listing not found")
+        
+    except HTTPException:
+        raise
+    except Exception as e:
+        metrics_registry.increment("rpc_marketplace_get_errors_total")
+        raise HTTPException(status_code=500, detail=str(e))
+
+@router.delete("/marketplace/listing/{listing_id}", summary="Delete marketplace listing", tags=["marketplace"])
+async def marketplace_delete_listing(listing_id: str) -> Dict[str, Any]:
+    """Delete a marketplace listing"""
+    try:
+        metrics_registry.increment("rpc_marketplace_delete_total")
+        
+        # Find and remove listing
+        for i, listing in enumerate(_marketplace_listings):
+            if listing.get("listing_id") == listing_id:
+                _marketplace_listings.pop(i)
+                return {
+                    "listing_id": listing_id,
+                    "status": "deleted",
+                    "message": "Marketplace listing deleted successfully"
+                }
+        
+        raise HTTPException(status_code=404, detail="Listing not found")
+        
+    except HTTPException:
+        raise
+    except Exception as e:
+        metrics_registry.increment("rpc_marketplace_delete_errors_total")
+        raise HTTPException(status_code=500, detail=str(e))