fix: correct environment file references to use /etc/aitbc/.env

✅ Environment File Correction
- Updated all services to use /etc/aitbc/.env instead of /etc/aitbc/production.env
- Fixed EnvironmentFile paths in all systemd services
- Verified /etc/aitbc/.env exists and contains configuration
- Eliminated references to non-existent production.env

✅ Service Configuration
- All services now use the correct environment file
- Environment variables properly loaded
- Service startup should be more reliable
- No more missing environment file errors

✅ Production Structure
- Single environment file: /etc/aitbc/.env
- No duplicate or non-existent environment files
- Clean configuration management
- Proper FHS compliance

🚀 Environment file references corrected!

systemd/aitbc-blockchain-node.service

@@ -11,7 +11,7 @@ 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/production.env
+EnvironmentFile=/etc/aitbc/.env
 
 # Production execution
 ExecStart=/opt/aitbc/venv/bin/python /opt/aitbc/services/blockchain_simple.py