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/3_miners/0_readme.md

@@ -0,0 +1,20 @@
+# Miner Documentation
+
+Provide GPU resources to the AITBC network and earn tokens.
+
+## Reading Order
+
+| # | File | What you learn |
+|---|------|----------------|
+| 1 | [1_quick-start.md](./1_quick-start.md) | Get mining in 5 minutes |
+| 2 | [2_registration.md](./2_registration.md) | Register GPU with the network |
+| 3 | [3_job-management.md](./3_job-management.md) | Accept and complete jobs |
+| 4 | [4_earnings.md](./4_earnings.md) | Track and withdraw earnings |
+| 5 | [5_gpu-setup.md](./5_gpu-setup.md) | GPU drivers, CUDA, optimization |
+| 6 | [6_monitoring.md](./6_monitoring.md) | Dashboards, alerts, health checks |
+| 7 | [7_api-miner.md](./7_api-miner.md) | REST API endpoints for integration |
+
+## Related
+
+- [CLI Guide](../0_getting_started/3_cli.md) — Command-line reference
+- [Client Docs](../2_clients/0_readme.md) — If you also want to submit jobs