chore: standardize configuration, logging, and error handling across blockchain node and coordinator API

- Add infrastructure.md and workflow files to .gitignore to prevent sensitive info leaks
- Change blockchain node mempool backend default from memory to database for persistence
- Refactor blockchain node logger with StructuredLogFormatter and AuditLogger (consistent with coordinator)
- Add structured logging fields: service, module, function, line number
- Unify coordinator config with Database

docs/4_blockchain/7_monitoring.md

@@ -0,0 +1,89 @@
+# Node Monitoring
+Monitor your blockchain node performance and health.
+
+## Dashboard
+
+```bash
+aitbc-chain dashboard
+```
+
+Shows:
+- Block height
+- Peers connected
+- Mempool size
+- CPU/Memory/GPU usage
+- Network traffic
+
+## Prometheus Metrics
+
+```bash
+# Enable metrics
+aitbc-chain metrics --port 9090
+```
+
+Available metrics:
+- `aitbc_block_height` - Current block height
+- `aitbc_peers_count` - Number of connected peers
+- `aitbc_mempool_size` - Transactions in mempool
+- `aitbc_block_production_time` - Block production time
+- `aitbc_cpu_usage` - CPU utilization
+- `aitbc_memory_usage` - Memory utilization
+
+## Alert Configuration
+
+### Set Alerts
+
+```bash
+# Low peers alert
+aitbc-chain alert --metric peers --threshold 3 --action notify
+
+# High mempool alert
+aitbc-chain alert --metric mempool --threshold 5000 --action notify
+
+# Sync delay alert
+aitbc-chain alert --metric sync_delay --threshold 100 --action notify
+```
+
+### Alert Actions
+
+| Action | Description |
+|--------|-------------|
+| notify | Send notification |
+| restart | Restart node |
+| pause | Pause block production |
+
+## Log Monitoring
+
+```bash
+# Real-time logs
+aitbc-chain logs --tail
+
+# Search logs
+aitbc-chain logs --grep "error" --since "1h"
+
+# Export logs
+aitbc-chain logs --export /var/log/aitbc-chain/
+```
+
+## Health Checks
+
+```bash
+# Run health check
+aitbc-chain health
+
+# Detailed report
+aitbc-chain health --detailed
+```
+
+Checks:
+- Disk space
+- Memory
+- P2P connectivity
+- RPC availability
+- Database sync
+
+## Next
+
+- [Quick Start](./1_quick-start.md) — Get started
+- [Configuration](./2_configuration.md) - Configure your node
+- [Operations](./3_operations.md) — Day-to-day ops