feat: add multi-chain support to blockchain explorer and improve GPU review handling

- Add multi-chain configuration with devnet, testnet, and mainnet RPC URLs
- Add chain selector dropdown in explorer UI for network switching
- Add chain_id parameter to all API endpoints (chain/head, blocks, transactions, search)
- Add /api/chains endpoint to list supported blockchain networks
- Update blockchain explorer port from 3001 to 8016
- Update devnet RPC port from 8080 to 8026
- Add GPU reviews table

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

@@ -8,7 +8,7 @@ engine = create_engine(
     "sqlite:////home/oib/windsurf/aitbc/apps/coordinator-api/aitbc_coordinator.db",
     connect_args={"check_same_thread": False},
     poolclass=StaticPool,
-    echo=False
+    echo=True  # Enable SQL logging for debugging
 )