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/7_deployment/0_index.md

@@ -0,0 +1,20 @@
+# Deployment & Operations
+
+Deploy, operate, and maintain AITBC infrastructure.
+
+## Reading Order
+
+| # | File | What you learn |
+|---|------|----------------|
+| 1 | [1_remote-deployment-guide.md](./1_remote-deployment-guide.md) | Deploy to remote servers |
+| 2 | [2_service-naming-convention.md](./2_service-naming-convention.md) | Systemd service names and standards |
+| 3 | [3_backup-restore.md](./3_backup-restore.md) | Backup PostgreSQL, Redis, ledger data |
+| 4 | [4_incident-runbooks.md](./4_incident-runbooks.md) | Handle outages and incidents |
+| 5 | [5_marketplace-deployment.md](./5_marketplace-deployment.md) | Deploy GPU marketplace endpoints |
+| 6 | [6_beta-release-plan.md](./6_beta-release-plan.md) | Beta release checklist and timeline |
+
+## Related
+
+- [Installation](../0_getting_started/2_installation.md) — Initial setup
+- [Security](../9_security/) — Security architecture and hardening
+- [Architecture](../6_architecture/) — System design docs