- Move EnvironmentFile from /opt/aitbc/.env to /etc/aitbc/blockchain.env in all systemd services
- Add main() entry point function to CLI for package installation compatibility
- Update aitbc-blockchain-node.service, aitbc-blockchain-node-dev.service
- Update aitbc-blockchain-rpc.service
- Update aitbc-blockchain-sync.service, aitbc-blockchain-sync-dev.service
This aligns with Linux filesystem hierarchy standards where /etc/ is the proper