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/1_quick-start.md

@@ -0,0 +1,37 @@
+# Miner Quick Start
+
+**5 minutes** — Register your GPU and start earning AITBC tokens.
+
+## Prerequisites
+
+- NVIDIA GPU with 16GB+ VRAM (V100, A100, RTX 3090+)
+- Python 3.10+, CUDA drivers installed
+- 50GB+ storage, stable internet
+
+## 1. Install & Configure
+
+```bash
+pip install -e .                                        # from monorepo root
+aitbc config set coordinator_url http://localhost:8000
+export AITBC_API_KEY=your-key
+```
+
+## 2. Register & Start
+
+```bash
+aitbc miner register --name my-gpu --gpu v100 --count 1
+aitbc miner poll                                         # start accepting jobs
+```
+
+## 3. Verify
+
+```bash
+aitbc miner status                                       # GPU status + earnings
+aitbc wallet balance                                     # check token balance
+```
+
+## Next
+
+- [2_registration.md](./2_registration.md) — Advanced registration options
+- [3_job-management.md](./3_job-management.md) — Job acceptance and completion
+- [5_gpu-setup.md](./5_gpu-setup.md) — GPU driver and CUDA setup