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/0_getting_started/3_cli.md

@@ -0,0 +1,73 @@
+# CLI Usage
+
+## Setup
+
+```bash
+pip install -e .                                    # from monorepo root
+aitbc config set coordinator_url http://localhost:8000
+export AITBC_API_KEY=your-key                       # or use --api-key
+```
+
+## Global Options
+
+| Option | Description |
+|--------|-------------|
+| `--url URL` | Coordinator API URL |
+| `--api-key KEY` | API key for authentication |
+| `--output table\|json\|yaml` | Output format |
+| `-v / -vv / -vvv` | Verbosity level |
+| `--debug` | Debug mode |
+
+## Command Groups
+
+| Group | Key commands |
+|-------|-------------|
+| `client` | `submit`, `status`, `list`, `cancel`, `download`, `batch-submit` |
+| `miner` | `register`, `poll`, `mine`, `earnings`, `deregister` |
+| `wallet` | `balance`, `send`, `stake`, `backup`, `multisig-create` |
+| `auth` | `login`, `logout`, `token`, `keys` |
+| `blockchain` | `status`, `blocks`, `transaction`, `validators` |
+| `marketplace` | `gpu list`, `gpu book`, `orders`, `reviews` |
+| `admin` | `status`, `jobs`, `miners`, `audit-log` |
+| `config` | `set`, `show`, `profiles`, `secrets` |
+| `monitor` | `dashboard`, `metrics`, `alerts`, `webhooks` |
+| `simulate` | `workflow`, `load-test`, `scenario` |
+
+## Client Workflow
+
+```bash
+aitbc wallet balance                                # check funds
+aitbc client submit --prompt "What is AI?"          # submit job
+aitbc client status --job-id <JOB_ID>               # check progress
+aitbc client download --job-id <JOB_ID> --output ./ # get results
+```
+
+## Miner Workflow
+
+```bash
+aitbc miner register --name gpu-1 --gpu a100 --count 4
+aitbc miner poll                                    # start accepting jobs
+aitbc wallet balance                                # check earnings
+```
+
+## Configuration
+
+Config file: `~/.aitbc/config.yaml`
+```yaml
+coordinator_url: http://localhost:8000
+api_key: your-api-key
+output_format: table
+log_level: INFO
+```
+
+## Troubleshooting
+
+| Problem | Fix |
+|---------|-----|
+| Auth error | `export AITBC_API_KEY=your-key` or `aitbc auth login` |
+| Connection refused | Check coordinator: `curl http://localhost:8000/v1/health` |
+| Unknown command | Update CLI: `pip install -e .` from monorepo root |
+
+## Full Reference
+
+See [5_reference/1_cli-reference.md](../5_reference/1_cli-reference.md) for all 90+ commands with detailed options.