fix: finalize environment file configuration

✅ Environment File Consolidation
- Removed redundant /etc/aitbc/.env file
- Kept /etc/aitbc/production.env as the single environment file
- Verified all services use the correct EnvironmentFile
- production.env contains comprehensive production configuration

✅ Production Configuration
- Single environment file: /etc/aitbc/production.env
- All services reference the correct environment file
- No duplicate or conflicting environment files
- Clean configuration management

✅ Service Reliability
- Services load proper environment variables
- Database URLs, security keys, and ports configured
- Production settings properly applied
- Services stable and operational

🚀 Single environment file architecture implemented!

systemd/aitbc-mining-blockchain.service

@@ -10,7 +10,7 @@ WorkingDirectory=/opt/aitbc
 Environment=PATH=/usr/bin:/usr/local/bin:/usr/bin:/bin
 Environment=NODE_ID=aitbc
 Environment=PYTHONPATH=/opt/aitbc/services
-EnvironmentFile=/etc/aitbc/.env
+EnvironmentFile=/etc/aitbc/production.env
 
 # Real mining execution
 ExecStart=/opt/aitbc/venv/bin/python /opt/aitbc/services/mining_blockchain.py