refactor: merge .env.production into central .env and standardize paths

- Merge blockchain-node/.env.production into central /opt/aitbc/.env
- Update all blockchain paths to use standardized /var/lib/aitbc/ structure
- Remove separate .env.production file (merged into central config)
- Update systemd services to remove references to .env.production
- Standardize Coordinator API paths and RPC port (8006)
- Add trusted_proposers setting for follower nodes
- Update multi-node workflow to reflect merged configuration
- Use aitbc1genesis as default proposer in central .env
- All services now use single central .env file with standardized paths

This eliminates configuration file duplication and ensures consistent
directory structure across all AITBC services.

systemd/aitbc-blockchain-p2p.service

@@ -9,7 +9,6 @@ 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
-EnvironmentFile=/opt/aitbc/apps/blockchain-node/.env.production
 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}
 Restart=always
 RestartSec=5