fix: update blockchain monitoring configuration and convert services to use venv python

Blockchain Monitoring Configuration:
✅ CONFIGURABLE INTERVAL: Added blockchain_monitoring_interval_seconds setting
- apps/blockchain-node/src/aitbc_chain/config.py: New setting with 10s default
- apps/blockchain-node/src/aitbc_chain/chain_sync.py: Import settings with fallback
- chain_sync.py: Replace hardcoded base_delay=2 with config setting
- Reason: Makes monitoring interval configurable instead of hardcoded

✅ DUMMY ENDPOINTS: Disabled monitoring

systemd/aitbc-blockchain-p2p.service

@@ -9,7 +9,8 @@ Group=root
 WorkingDirectory=/opt/aitbc/apps/blockchain-node
 Environment=PATH=/usr/bin:/usr/local/bin:/usr/bin:/bin
 Environment=PYTHONPATH=/opt/aitbc/apps/blockchain-node/src:/opt/aitbc/apps/blockchain-node/scripts
-ExecStart=/usr/bin/python3 -m aitbc_chain.p2p_network --host ${p2p_bind_host} --port ${p2p_bind_port} --redis ${gossip_broadcast_url} --node-id ${proposer_id}
+EnvironmentFile=/etc/aitbc/blockchain.env
+ExecStart=/opt/aitbc/venv/bin/python -m aitbc_chain.p2p_network --host ${p2p_bind_host} --port ${p2p_bind_port} --redis ${gossip_broadcast_url} --node-id ${proposer_id}
 Restart=always
 RestartSec=5
 StandardOutput=journal